There is provision of an electrostatic chuck for supporting a substrate and an edge ring including a first region, a second region, an electrode provided in the second region, and an elastic member. The first region includes a first top surface and is configured to hold the substrate that is placed on the first top surface. The second region extends in a circumferential direction of the first region so as to surround the first region. The second region includes a second top surface, and is configured to support the edge ring placed on the second top surface. The first top surface and the second top surface extend along a single flat plane. A part of the edge ring is accommodated in a space provided between the first region and the second region, and the elastic member is disposed between the part of the edge ring and the electrostatic chuck.