Provided is an assistance device that a person being assisted can easily engage with. A side insertion portion (522a) of a side support member (52) is provided such that when a torso support member (51) is positioned in an engagement position in relation to a person being assisted (M) who is in a sitting posture, the side insertion portion is in an engagement position of extending from the torso support member (51) towards the rear of the person being assisted (M). When the torso support member (51) tilts forward to cause the person being assisted (M) to transition to a standing posture, the side insertion portion (522a) is provided so as to be in a standing posture of extending from the torso support member (51) towards the upper rear of the person being assisted (M).
