Provided is a foam dispenser that is capable of preventing water or the like from entering an air cylinder. In the foam dispenser, a liquid piston is fitted in a liquid cylinder portion, and an air piston is fitted in an air cylinder portion, and upward and downward displacement of the actuator causes a content liquid within the liquid cylinder portion and air within the air cylinder portion to be mixed and foamed and then dispensed from a nozzle, and a partition wall is provided with an ambient air introducing hole, and from at least a portion of a hole periphery of the ambient air introducing hole, a water entering prevention side wall portion stands for preventing water from entering the ambient air introducing hole.