A stress state evaluation apparatus includes an acquisition section that acquires living body data from each individual included in a group, a first specification section that specifies a non-stress state of each individual based on the living body data acquired from the acquisition section, an adjustment section that adjusts a determination reference of a stress state of each individual based on the non-stress state of each individual specified in the first specification section, a second specification section that specifies the stress state of each individual using the determination reference adjusted by the adjustment section based on the living body data acquired from the acquisition section, and an operation section that operates a stress state of the group based on the stress state, which is specified by the second specification section, of each individual.
