A matrix type display device including: a photosensor, provided in a display region, for outputting a signal corresponding to an intensity of light emitted to the photosensor; a TFT of n-channel type, the TFT serving as a source follower including a gate to which the signal is inputted; and light intensity detecting means for detecting the intensity of the light by detecting an output of the source follower, which is the TFT. In at least one embodiment, the TFT includes a drain to which a first pulse signal (Vpulse2) having a first pulse is inputted, the first pulse rising from a low level to a high level in a state where the signal is inputted to the gate of the TFT.