This paper presents design studies on hybrid excitation flux switching motor (HEFSM) that can compete with an interior permanent magnet synchronous motor (IPMSM) installed on TOYOTA PRIUS-2010. A stator of the HEFSM consists of not only laminated core and three-phase armature windings, but also field excitation coils and permanent magnets as field mmf sources. This machine makes it possible to vary its field flux by combining the two different mmf sources and thus, the name is capped by "hybrid excitation" as a variable field flux motor. The first trial manufacturing of HEFSM has been built for tests to assess its drive performances. Based on analysis of the test results, design refinements on the first test motor are examined to make the second trial manufacturing. Various experimental test results using the second test motor demonstrate that drive performances of the HEFSM are comparable to those of the PRIUS's IPMSM.