A flow rate switching mechanism including: a first section including: a first housing with a passage internally bored through, the passage having a narrowed portion at a distance from one end of the passage, and the narrowed portion having a smaller cross-sectional area than the cross-sectional area of the passage at the one end; a capillary having an internal passage having a smaller cross-sectional area than the cross-sectional area of the narrowed portion; and a hermetic support member supporting the capillary and to provide a seal; a second section having a second housing identical in shape to the first housing, without having the capillary and the hermetic support member; and a three-way valve being alternatively switchable between a first state in which the outlet end is connected to the first inlet end and a second state in which the outlet end is connected to the second inlet end.