A substrate treating apparatus includes a plurality of solution treating units for performing solution treatment of substrates, and a plurality of individual gas supply devices provided to correspond individually to the solution treating units, each for supplying gas at a variable rate only to one of the solution treating units. The solution treating units perform the solution treatment by supplying treating solutions to the substrates. The individual gas supply devices supply gas only to the solution treating units corresponding thereto. The individual gas supply devices supply the gas at adjustable rates to the solution treating units. The rate of gas supply to the solution treating units can therefore be varied for each solution treating unit.