Various kinds of periodical phenomena are observed in the natural world and in the social systems. Even in apparel fashion trends, people feel some periodical changes exist. This paper presented a trial to qualitatively characterize such a periodicity which appeared in apparel fashion trends. For this purpose, numerical data for the length of ladies jackets and skirts proposed in a popular fashion magazine published in Japan from 1960 to 1998 were used. Data were treated with some mathematical techniques including Fourier transformation analysis, self-correlation analysis and common statistical methods. Results obtained are as follows; 1) Comparing the distribution of length for clothes proposed in a given year with the length of the clothing selected by a person as being representative of the year, it was clarified that the length of the representative clothing selected by the person coincided with the mode value for the distribution. 2) Three major changes in the length of jackets and skirts were found over the years, the first change after a periodic time of 10 years, the second after 20 years and the third after 40 years. The change which occurred after 10 years periodicity was the most profound one. 3) The 10-year periodicity may be correlated with the period of use of apparel, while 20-year periodicity may be connected to the length of time which takes for women to develop a mature fashion sense. The 40-year periodicity remains unclear, but it covers two generations and, therefore, is long enough for the revival of an old fashion as a new fashion.