A chain inlet/outlet, from which a load chain on a load side is hauled in or paid out, has a first guide groove having a first longitudinal groove and a first lateral groove. The chain inlet/outlet also has a second guide groove that is provided on a deeper side of a body part than the first guide groove is and has a second longitudinal groove and a second lateral groove. The first guide groove has narrowed parts that determine, when each link of the load chain is pulled in, into which of the first longitudinal groove and the first lateral groove the link is introduced, and expanded groove parts having a width larger than the groove width of the narrowed parts and provided on the outer side, farther away from the center of the chain inlet/outlet than the narrowed parts.