To accurately detect a full stacked state of sheets within a tray even when delivery intervals of the sheets are short.

A sheet delivery device 100 includes: a tray 11 on which sheets are stacked; a delivery mechanism for delivering sheets one by one; a pendulum mechanism 2 in which a weight 20 is lifted up by sheets to be delivered or sheets on the tray 11; signal transmitting means for transmitting a first signal when the weight 20 is located at a position lower than a reference position and transmitting a second signal when the weight 20 is located at a position equal to or higher than the reference position; and a control part 80 controlling the delivery mechanism and receiving the signals transmitted by the signal transmitting means. When sheets are continuously delivered, the control part 80 determines whether the signal transmitting means is in a first state where it continuously transmits the second signal for a fixed time or longer or in a second state where it transmits the first signal within the fixed time after transmission of the second signal. When the first state is determined, sheet delivery is stopped only for a predetermined time, and when the second signal is continuously transmitted within the predetermined time, it is determined that sheets are stacked up to height equal to or higher than the reference position.