A body weight support device comprising: a body attachment part including a waist belt part attachable to a body of a user; a floor contact part provided contactably on a floor, a leg link part including an upper leg link part, a knee joint part and a lower leg link part provided along a leg of the user for connecting said body attachment part to said floor contact part through the knee joint part, the upper leg link part being connected to the lower leg link part through the knee joint part and the lower leg link part being connected to the floor contact part; a crotch joint part actuator; a knee joint part actuator for driving said knee joint part; and a control unit for controlling driving of said knee joint part actuator, said control unit driving said knee joint part actuator to drive the knee joint part to generate torque between the upper leg link part and lower leg link part, so that said leg link part gives a body weight support force to said user through said body attachment part, the body weight support force being a force for partially supporting weight of the user, the body weight support force being given to the user through the crotch joint part actuator, characterised in that: the leg link part is configured to be kept bent while the user is wearing said body weight support device, the upper leg link part, the knee joint part and the lower leg link part being adjusted in length to prevent the upper leg link part and the lower leg link part from becoming in line and to prevent the lower leg link part from bending about the knee joint part to a forward side of the in line position relative to a direction in which the user is facing. a body attachment part including a waist belt part attachable to a body of a user; a floor contact part provided contactably on a floor, a leg link part including an upper leg link part, a knee joint part and a lower leg link part provided along a leg of the user for connecting said body attachment part to said floor contact part through the knee joint part, the upper leg link part being connected to the lower leg link part through the knee joint part and the lower leg link part being connected to the floor contact part; a crotch joint part actuator; a knee joint part actuator for driving said knee joint part; and a control unit for controlling driving of said knee joint part actuator, said control unit driving said knee joint part actuator to drive the knee joint part to generate torque between the upper leg link part and lower leg link part, so that said leg link part gives a body weight support force to said user through said body attachment part, the body weight support force being a force for partially supporting weight of the user, the body weight support force being given to the user through the crotch joint part actuator, characterised in that: the leg link part is configured to be kept bent while the user is wearing said body weight support device, the upper leg link part, the knee joint part and the lower leg link part being adjusted in length to prevent the upper leg link part and the lower leg link part from becoming in line and to prevent the lower leg link part from bending about the knee joint part to a forward side of the in line position relative to a direction in which the user is facing.