The purpose of this study was to examine the developmental process of pragmatic negation from the sensorimotor interaction to the early linguitic communication. The data for this case study were the longitudinal diary records of my daughter A, from her birth to 24 months of age. The data for analysis were 396 nonverbal and verbal episodes of pragmatic negation. Resultant findings: (1) The development of media used for pragmatic negation The earliest emergence of media she used was crying with nondirective activities. The second was exclusive direct actions for an object or person, the third was the symbolic use of ritual headshaking gesture, and the last was the verbal negation. The abovementioned negative media were not only the change from gesture to language, but the later media were combined to the earlier media, then building more effective communications. (2) The acquisition of head gestures Nodding and shaking the head are a type of symbolic behaviour similar to affirmative/negative particles, and the establishment of these gestures was at 1: 1. (3) The process of the functional differentiation of pragmatic negation It could clearly be seen that function preceded from in the development of negation. In this study five-functional categories of negation were suggested: 1. exclusive rejection, 2. rejective expression of request for supportive action, 3. denial, 4 nonexistence, 5. prohibition. Rejection was the first function in which negations were used for, the first topics of negation were concretely present in the child's immediate world of activity and transcended the here and now only when negative comments came up. About a year later, other types of negation such as denial, non-existence, prohibition appeared. In the later negation contexts, the topic of negation had transcended on the spot. The negation acquired later was based on one's judgment about unfulfilled expectation or presupposition. The more mature use of unfulfilled expectation provided an important insight into the development of pragmatic negation. So, the developmental sequence of negation from emotional to declarative was confirmed. (4) Form-Function Mapping Some lexical items, iya ( iyayo , iyada ), attspu , metts (a baby-talk), nai , ii , chigau , were used to signal exclusive rejection. Lexical item nai ( inai ) signified nonexistance, nai expressed denial, and dame ( metts ) indicated prohibition. In early stage, nai was overregularized to almost all functions to negation. (5) The developmental strategies of negative lexicon Strategy 1. To intend negation, the specialized vocal must be used. Strategy 2. The negative operator is used independently and negates the whole proposition. Strategy 3. The negative operator has fixed location, and in Japanese, it is put at the last part of the utterances. Strategy 4. To combine the words, the negative operator is only added to other linguistic items. Strategy 5. To combine the words, other linguistic items are inflected, and then added to the negative operator. Strategy 6. To combine the words, other linguistic items (nouns and nominal adjectives) are followed by the negative form janai .