A cupsole, that a user wears and is fixed to a foot sole plate of a walking assistance apparatus that assists a motion of a leg part of the user, includes: a main body part on which the user's foot is placed; and an index member that is fixed to the main body part and is configured to determine an attachment position with respect to a reference index provided in the foot sole plate, the attachment position varying for each user, in which the index member can be attached to or detached from the main body part.