The present invention provides an automatic foam soap dispenser used for single soap reservoir which is pressed from top to down. The automatic foam soap dispenser includes a covering housing opened downwardly for accommodating a pressing-typed soap reservoir, a control circuit board, a motor, and a sensor. The soap reservoir has a pressing head at the top thereof, the pressing head is communicated with a connecting head, and the connecting head has an extension pipe to communicate with a foam nozzle, which is mounted at the bottom of the covering housing. Moreover, an extension fixing board is extended inside the covering housing for mounting a transmission gear set, which is driven by the motor to turn, and a swinging pressing board, wherein the transmission gear set has a cam, and a first end of the swinging pressing board is pivotally connected to the cam and the transmission gear set, and a second end of the swinging pressing board is leaned on the pressing head or the connecting head. Accordingly, the present invention not only complies with the usual practice of downward soap output, but also prolongs the lifetime of the soap reservoir and the soap dispenser, and the problem of soap dropping caused from the remaining foam soap is also solved.