An assist device includes a first body-worn unit; second body-worn units; an actuator; a controller configured to obtain an assist parameter that determines assist torque to be generated, and perform control to operate the actuator at an output based on the assist parameter; and a tilt angle detection part configured to obtain tilt angle information on a tilt angle of an upper body of a user. The actuator includes arms; and swing angle detection parts configured to obtain swing angle information on swing angles of the arms that represent angles formed by the upper body and thighs of the user. The controller is configured to obtain the assist parameter based on the swing angle information and the tilt angle information.