A countertop automatic foam soap dispenser includes an automatic foam soap dispenser body, a soap liquid container, a circular connecting tube and a battery compartment. The soap liquid container is filled with an appropriate quantity of liquid soap. The battery compartment supplies electric power to the automatic foam soap dispenser body. The automatic foam soap dispenser body is passed through the circular connecting tube by a soap transmission tube and installed to the bottom inside the soap liquid container. The automatic foam soap dispenser body includes a foam soap valve, a control circuit board, a sensor, a motor controlled by the control circuit board, and a transmission gear set. When a user's hand approaches a sensor of the automatic foam soap dispenser body, the motor drives a cam of the transmission gear set to rotate and compress a foam soap valve to supply the appropriate quantity of foam soap.