A standing motion assist device includes a support mechanism attached to a leg of a user to assist the user with motion, a sensor including first and/or second sensors that measure and output posture information and myoelectric potentials of the user, respectively, the sensor outputting measurement data including first measurement data measured after a sitting motion of the user sitting in a chair starts and second measurement data measured after the sitting motion ends, a memory that stores the measurement data, and a processor that controls the support mechanism. The processor detects the sitting motion and identifies the chair type based on the first measurement data, detects the start of a motion of the user standing from the chair based on the second measurement data, and outputs assist information corresponding to the identified chair type and used by the support mechanism to assist the user with standing.
