In one embodiment, a substrate processing liquid contains phosphoric acid as a primary component and contains water and ketone. In another embodiment, a substrate processing method includes processing a substrate in a substrate processing bath with a substrate processing liquid containing phosphoric acid, water and ketone. The method further includes discharging the substrate processing liquid from the substrate processing bath to a circulating flow channel, heating the substrate processing liquid flowing through the circulating flow channel at a temperature between 50° C. and 90° C., and supplying the substrate processing liquid again from the circulating flow channel to the substrate processing bath to circulate the substrate processing liquid under heating.