A portable, walk in type bathtub includes an entrance and a door attached thereto to allow someone to walk into the bathtub without stepping over a wall. The position of the magnetic pair along the strap can be changed as well as the number of magnetic pairs on the strap. By using an apparatus for manufacturing a semiconductor device including a plurality of treatment chambers, a treatment can be made without being exposed to a clean room atmosphere in an interval between respective treatment steps, and it becomes possible to keep the interface of the respective films constituting the TFT clean.