A pre-baking apparatus for heating a substrate upstream of a process tool is adapted to be connected to an EFEM (equipment front end module) and includes: a chamber which has a front face with multiple slots arranged in a height direction of the chamber, and which is divided into multiple compartments extending from the multiple slots, respectively, toward a rear end of the chamber for loading and unloading substrates; and a connecting frame for connecting the chamber to the process tool. The multiple compartments are separated from each other by a divider plate and provided with heaters for heating the multiple compartments, and each compartment has a gas injection port for blowing a hot inert gas over the substrate placed therein toward the slot.