A gesture detecting apparatus prepares time series data of coordinates of specific part of object gesturing, calculates velocity vector of the specific part from the time series data of coordinates, to obtain time-series velocity vectors, detects dynamic periods when displacement per unit time of the specific part is larger than predetermined value, based on the time-series velocity vectors, acquires each representative velocity vector from velocity vectors in each dynamic period, stores the each representative velocity vector corresponding to the each dynamic period in memory, calculates first intersection angle of two representative velocity vectors stored in the memory, the two representative velocity vectors corresponding to two successive dynamic periods, and detects that the motion of the specific part is reciprocating motion when the first intersection angle is larger than first threshold value.