A foot base for assistive device includes a base body having a receiving space, a top opening and multiple foot pads; a flexible sleeve disposed in the receiving space to protrude from the base body; a support rod having a lower end received in the receiving space and provided with a stop plate, and an upper end extended through the flexible sleeve for joining with an assistive device; and a spring received in the receiving space and fitted around the flexible sleeve with two ends pressed against the stop plate and an edge of the opening. With the flexible sleeve and the spring, the support rod can conically swing relative to a centerline of the foot base, allowing the assistive device to swing forward and backward when a user shifts body gravity center during walking. The foot pads enable the foot base to provide anti-skidding, buffering and shock-absorbing effects.