An apparatus for heating a substrate includes: a stage including at least one resistance heater that heats the substrate placed thereon; a temperature detector for detecting a heating temperature of the substrate; a temperature calculator for calculating the heating temperature based on a resistance value of the at least one resistance heater; a power controller for performing a power control with respect to a first power to be supplied to the at least one resistance heater such that the heating temperature becomes close to a first preset temperature by switchably applying a phase control and a zero-cross control; and a controller for switching the power control of the power controller to the phase control or the zero-cross control.