In a substrate processing apparatus of the present disclosure, a bearing member includes a decaying mechanism provided with a connecting shaft inserted therein and configured to decay radicals or ions; a first member configured to cover the decaying mechanism; and a second member disposed at the connecting shaft and provided with the connecting shaft inserted therein while being in contact with a sealing member. Further, an end of the first member and an end of the second member are connected to be engaged with each other, an invasion path is formed to allow the radicals to invade from the connected portion of the end of the first member and the end of the second member, and the invasion path is formed to be folded back in an extending direction of the connecting shaft. The sealing member is made of a material having a tensile strength larger than 12.1 MPa.