A cellulose saccharification method including an introduction step of introducing water, a raw material containing cellulose, and a surfactant into a saccharification vessel so as to obtain a liquid mixture, an agitation step of agitating the liquid mixture due to rotation of an impeller portion, and a detection step of detecting a torque sensed by the impeller portion, wherein regarding the agitation step, after agitation is performed until an amount of the torque changed in a unit time period becomes less than or equal to a predetermined value, when the torque is more than or equal to a threshold value, the surfactant is additionally introduced into the liquid mixture, or when the torque is less than the threshold value, a pH adjuster and an enzyme are introduced into the liquid mixture.
