A substrate conveyance mechanism includes conveyance units and a clamp mechanism. The conveyance units include a working unit corresponding to a working area for types of substrates having different sizes of length taken as objects, an area length of the working area being variable in accordance with the sizes of length, and a stand-by unit corresponding to a stand-by area for the substrate to be carried-in to the working area. The clamp members include commonly used first clamp members and second clamp members which are attachable and detachable and are selectively used in accordance with the sizes of length of the plurality of types of substrates in addition to the first clamp members.