A substrate treating apparatus includes a treating unit for treating substrates, a piping for supplying a treating liquid to the treating unit, a heater mounted on the piping, an electronic thermal unit mounted on the piping in series with the heater, a temperature sensor for measuring a temperature of the treating liquid, and a controller for controlling the heater and the electronic thermal unit. The controller sets a first temperature control mode for performing a room temperature control using the electronic thermal unit when the temperature measured by the temperature sensor is below a predetermined boundary temperature between room temperature and high temperature, and for performing a high temperature control with the heater when the temperature measured by the temperature sensor is above the predetermined boundary temperature between room temperature and high temperature. The controller sets a second temperature control mode for performing a heating control using the heater and the electronic thermal unit to heat the treating liquid when a difference between the temperature measured by the temperature sensor and a target temperature at least corresponds to a first specified value set beforehand. Further, the controller sets the first temperature control mode when, after the second temperature control mode is set, the difference between the temperature measured by the temperature sensor and the target temperature becomes less than a second specified value set beforehand.