An activity amount calculation system (100) includes a plurality of detection units (D1, D2) and an activity amount calculation device (10). The plurality of detection units (D1, D2) detect a resident and output detection signals when the resident passes through doorways of a plurality of rooms. The calculation device (10) includes a calculation unit (11) and a summation unit (12). Upon detection of the resident by the detection units (D1, D2), the calculation unit (11) calculates an activity amount of the resident based on relationships between detection units and reference activity amounts. The summation unit (12) repeatedly calculates a total activity amount of the resident in a predetermined period by summing activity amounts calculated by the calculation unit (11).