Electrostatic chuck

An electrostatic chuck includes a ceramic dielectric substrate and a base plate. The base plate includes a communicating path configured to allow a coolant to pass. The communicating path includes a first flow path part having a pair of side surfaces along a first direction. The first direction is along a flow of the coolant. When viewed along a stacking direction, one side surface of the pair of side surfaces includes a plurality of convex portions and a plurality of concave portions. The plurality of convex portions is convex in a second direction. The second direction is perpendicular to the first direction. The second direction is from the other side surface toward the one side surface of the pair of side surfaces. The plurality of concave portions is convex in an opposite direction of the second direction.