Automatically in an emergency to be decoupled fluid coupling

A fluid coupling in which a male clutch is brought into a state with a fixed connection in which the male coupling is firmly connected with a female coupling member and is held at a position with a fixed connection relative to the female coupling member is provided, wherein the condition with fixed connection is broken if an excessive voltage to a fluid flow line is applied, in which the fluid coupling member is fitted, so that the voltage on the male and female coupling members acting to separate them. A first valve is provided between the outer surface of the male coupling member and the inner surface of the female coupling member and is slidably engaged therewith. The first valve has a through-hole having an outer end opening on its outer side and an inner end opening on its inner side in order to connect fluidly the fluid passages of the male and female coupling members.