A process chamber door for closing or opening an entrance of a process chamber through which a substrate to be process is loaded includes a seal plate including a front surface and a rear surface opposite to each other in a first direction, a connection block connected to the rear surface of the seal plate and including a central portion and two side portions connected to the rear surface of the seal plate, and a shaft connected to the central portion of the connection block. The connection block includes a first hinge groove and a second hinge groove. The first hinge groove is exposed at a bottom surface and a side surface of the connection block and the second hinge groove is exposed at an upper surface and the side surface of the connection block.