The purpose of the present study was to investigate developmental progresses on the mental rotation in children. The subjects were 64 second-grade, 65 fourth-grade, and 62 sixth-grade primary-school children, and 44 university students. Four kinds of stimuli, that is, 2, 5, “よ”, “ろ” were used. These stimuli were rotated at an angle of 0°, 60°, 120°, 180°, 240° and 300° and presented to the subjects. They were asked whether the stimulus presented was the same as the non-rotated one. The results showed that there were developmental progresses in the correct responses and the reaction times by grades. Also, the relations between mental rotations and mental abilities showed that the strategies used in this problem were different by grades. Lower grade children were inclined to use spatial abilities while higher grade children were apt to use numerical and verbal abilities.