In one embodiment, a substrate transfer device is equipped with a chamber wall, a table, a linear motor transfer mechanism, an optical window, and a laser measuring instrument. The chamber wall defines a transfer space. The table is housed within the transfer space. It is possible for a substrate to be loaded on the table. The linear motor transfer mechanism moves the table within the transfer space, by a linear motor. The optical window is installed between the transfer space and the space to the outside of the transfer space. For example, the optical window is disposed so as to seal off an opening defined in the chamber wall. The laser measuring instrument irradiates a laser light through the optical window and towards the table, receives reflected light from the table, and measures the position of the table.