Provided is an assistance device in which a person being assisted can easily get on. The side insertion part (522a) of the side support member (52) is covered from the body support member (51) when the body support member (51) is located at the boarding position with respect to the person being assisted in the sitting position (M). It is provided so that it may become the boarding attitude position extended toward back of a helper (M). When the trunk support member (51) tilts forward, the side insertion part (522a) moves the person being assisted (M) from the trunk support member (51) to the person being assisted (M). It is provided so that it may become the standing posture extended toward the upper back.被介助者が楽に乗り込むことができる介助装置を提供する。脇支持部材（５２）の脇挿入部（５２２ａ）は、胴体支持部材（５１）が座位姿勢の被介助者（Ｍ）に対して乗り込み位置に位置するときに、胴体支持部材（５１）から被介助者（Ｍ）の後方に向かって延びる乗り込み姿勢となるように設けられる。脇挿入部（５２２ａ）は、胴体支持部材（５１）が前方に傾動することにより被介助者（Ｍ）を立位姿勢に移行させる際に、胴体支持部材（５１）から被介助者（Ｍ）の上後方に向かって延びる立ち上がり姿勢となるように設けられる。
