A viscous fluid type heater including a stator having a stationary surface and a rotor having a rotary surface. The rotary surface is opposed to the stationary surface to define a clearance therebetween for the accommodation of a viscous fluid. A circulating fluid flows through a heat exchanging chamber. The rotor rotates about its axis and shears the viscous fluid to produce heat. The heat is transmitted to the circulating fluid from the viscous fluid. The rotary surface is inclined with respect to the rotor axis. The stationary surface is inclined in conformity with the rotary surface.
