To provide a substrate treating apparatus and a treatment chamber washing method that can prevent a substrate from being contaminated with washing liquid for washing the inside of a treatment chamber.

In the treatment chamber 2, a first washing liquid discharge nozzle 32 for discharging washing liquid, a second washing liquid discharge nozzle 33 for discharging washing liquid, and an N2 gas discharge nozzle 34 for discharging N2 gas are provided on one side (right side in Fig.) by above a top of a shutter 18 in a closed state (in a horizontal direction along a side wall 1). SPM sticking on the top of the shutter 18 is washed away by the washing liquid. Washing liquid used for the washing is removed by N2 gas.