A walking assistance device has a drive mechanism for driving a third joint of a leg link of the walking assistance device, the drive mechanism including a crank arm secured to a lower link member and a linear-motion actuator which has a linear-motion output shaft connected to the crank arm. The angle formed by a straight line connecting a joint axis of the third joint and a connecting portion of the linear-motion output shaft relative to the crank arm and a straight line which passes the connecting portion and which is parallel to the axial center of the linear-motion output shaft changes from an angle closer to the straight angle toward an angle closer to the right angle as the flexion degree of the leg link is increased from a flexion degree corresponding to a state wherein a user is in an upright posture.