To provide an induction heater for heating a large container having a round bottom shape and facilitated in the quick washing thereof with water after a heating process.

In this induction heater, the top surface of a rack 2 is formed into a heating surface 3, on which a metal container 5 having a round bottom and housing a material to be processed is placed, for electromagnetic induction heating. This heating surface 3 is formed into a nearly recessed mirror shape provided with a through-hole 4 at the center thereof, and a sensor 6 for sensing placement of the metal container 5 to indicate electrifying to the heating surface 3 is arranged in a space of the through-hole 4.