The present invention facilitates adjustment of the strength of an elastic orthotic that assists the movement of an orthotics user by whom the elastic orthotic is worn. This calculation device for calculating the optimum elastic strength of an elastic orthotic comprises a storage unit in which elastic strength and kinematic properties established through experiments in which a plurality of people wear elastic orthotics are stored in advance, and a mathematical optimization processing unit that calculates the optimal elastic strength on the basis of a prescribed evaluation index on the basis of the kinematic constraint condition of an orthotics user and the elastic strength and kinematic properties.
