Induction heating cooktop

A cooktop of the induction heating method comprising:

• a top plate on which a cooking vessel is placed;
• a working coil configured to generate a magnetic field passing through the cooking vessel;
• an inverter configured to supply current to the working coil;
• a sensor configured to detect the temperature of the top plate;
• and
• a controller configured to identify a material of the cooking vessel using at least one of a change in a load impedance and a change in temperature, and determine whether the cooking vessel is in a preheated state based on at least one reference value that compares the change in the load impedance and the change in temperature, which are set differently for each material of the cooking vessel,
• wherein the controller, when the cooking vessel is in a preheated state, is configured to adjust an output to be lower than the output according to the set heat power.