A body movement detecting apparatus includes a measuring section which outputs, as at least one time-series signal, at least one result of measurement obtained by measuring body movement, a detecting section in which, after slicing off a part of the time-series signal output from the measuring section to generate a reference signal having a predetermined interval length from a predetermined position in the time-series signal, the detecting section detects the intensity of correlation between the reference signal and each different part of the time-series signal in the vicinity of the reference signal, the different part having the predetermined interval length, and a determining section which, on the basis of the detected intensity of correlation detected by the detecting section, performs one or both of determining whether or not the body movement is periodic, and determining the period of the body movement.