A bimetal fan clutch may include a disc-shaped rotor that is affixed to a shaft coupled with an engine between a lower case fixed to the shaft via a bearing and an upper case covering the lower case and having a space, an oil storage that is attached to one face of the rotor to be housed in the space and has a projection inserted into a central hollow part formed in the upper case, a bimetal oil valve that is provided inside the oil storage, wherein the bimetal oil valve changes its shape in response to heat transferred through a bimetal assembly mounted through the projection and thereby opens/closes a through-hole formed in the oil storage, and a return line that is formed in the lower case so that oil ejected to the space through the through-hole is collected into the oil storage.