PROBLEM TO BE SOLVED: To provide a tool which has a simple structure and efficiently reduces a burden of a helper supporting a user in standing-up/seating motion.SOLUTION: A support mechanism 2 including a gas spring 22 supports an armrest part 1. The support mechanism supports the armrest part in a lock state of the gas spring so as to change a posture between a normal posture and a leaning forward posture. The support mechanism supports the armrest part in a lock release state of the gas spring so as to move from a seating posture corresponding position T1 toward a standing posture corresponding position T2 in a front upper side while drawing an arc. Between the gas spring and the armrest part, a gas spring switch part is arranged which does not obstruct the lock state of the gas spring when the armrest part is in the normal posture and cancels the lock state of the gas spring when the armrest is in the leaning forward posture.SELECTED DRAWING: Figure 2
