A coupler system includes: a coupler main body attached to a longitudinal direction end of a carbody of a railcar so as to be rotatable in a yaw direction; a curvature information acquiring portion configured to acquire curvature information of a track, the railcar being located on the track; a control portion configured to determine a target rotation angle of the coupler main body in accordance with the acquired curvature information and output a rotation signal regarding the determined target rotation angle; and a rotation angle changing portion configured to rotate the coupler main body to the target rotation angle based on the output rotation signal. When the railcar is stopped or when the railcar is traveling at a coupling speed, the control portion outputs the rotation signal to start rotating the coupler main body.