An information processing apparatus (100) acquires information regarding a stride length (SL) of a subject and information regarding angles (θL and θR) of respective lower legs of the subject with respect to the ground in a case where both feet of the subject are grounded. The information processing apparatus (100) calculates angles (α and β) of respective knee joints of the subject and an angle (ϕ) of a hip joint of the subject that satisfy geometric constraints, derived from a structure of lower limbs of the subject in a case where both feet of the subject are grounded, based on the information regarding the stride length (SL) and the information regarding the angles (θL and θR). For example, the geometric constraint is a constraint that is geometrically derived based on a (polygon 110) that is formed by using each thigh, each lower leg, and the ground as sides and the hip joint, each knee joint, and a contact point between each lower leg and the ground as vertices, by using the structure of the lower limbs of the subject.
