The occurrence of trunk muscle contraction associated with body movement and the like is accurately and timely detected using pulse data. A trunk muscle contraction detection apparatus includes a change-component acquisition unit that extracts change-component data representing a change component of pulse-interval data, the change component regarding pulse intervals, a vibration-component removing unit that generates vibration-component removal data by removing, from the change-component data, a vibration component corresponding to periodic vibrations in the pulse-interval data, and a variation-component extraction unit that extracts a certain variation component from the vibration-component removal data, and determines the occurrence of trunk muscle contraction in accordance with the certain variation component, which has been extracted.
