A working posture holding device (10) includes: a lower back holding part (11) that holds a lower back of a user; a leg part (12a) that supports the lower back holding part, the leg part being rotatably connected to the lower back holding part, the leg part extending along a leg region of the user; a foot part (13a) that is connected to the leg part, the foot part contacting a ground to support the overall working posture holding device; a fixing part (14a) that fixes the leg part and the user to each other; and a locking mechanism (15a) that switches a state of the leg part between a “variable” state where a distance between a connection part to the lower back holding part and a connection part to the foot part is variable, and a “locked” state where the distance is fixed.