The invention relates to a vessel for embryoid formation used for forming embryoid bodies from ES cells easily without complicated technique, and to a method for forming embryoid bodies easily and efficiently using the vessel. A process for manufacturing the device is also described. The solenoid coil has a central axis coaxial with a central axis of the ESR microwave cavity, and orthogonal to a direction of a main magnetic field generated by the magnetic device. Because the scabbard collapses, and the injection molded case offers ample space not afforded in all existing blow molded chain saw cases, the scabbard can be placed inside the case during shipment reducing shipping cost and space required while in distribution. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.