YIG film microwave apparatus, utilising the ferrimagnetic resonance of a YIG film, comprises a YIG film microwave device (1) formed by a liquid phase epitaxial growth process and a photolithographic process, and a magnetic circuit (2) including permanent magnets (4) for applying a DC magnetic field to the YIG film microwave device (1). ). The Fe 3- ions of the YIG film are partially substituted by nonmagnetic ions to provide YIG film microwave apparatus with satisfactory temperature characteristics. The YIG film microwave apparatus is capable of operating stably over wide ranges of working frequencies and temperatures.