A plasma processing apparatus includes a processing chamber; a placing table disposed in the processing chamber to place a substrate thereon; an upper electrode facing the placing table; a member configured to adjust a temperature of the upper electrode; a first sensor provided within the member configured to adjust the temperature of the upper electrode, and configured to measure the temperature of the upper electrode; and a first sheet member, disposed between the upper electrode and the first sensor, having a relative dielectric constant of 2.4 or higher at a frequency of 1 MHz.