PURPOSE: To provide a high performance and compact pump by motor-driving a piston movable in a material chamber via a rotary head having an inclined guiding path and a coupling means including a driving member moved along the guiding path to alternately operate the piston.

CONSTITUTION: A fluid dispenser device 9 is driven by an electric motor to be reciprocated in a roughly hollow main body 202. A piston 206 defining a pump chamber 208 is provided between it and the main body 202, and a film 252 for expanding/shrinking the capacity of the pump chamber 208 communicated with a fluid source in an inlet opening 212 and with a discharge duct 21 in an outlet opening 333 is connected to the tip surface of the piston 206. In the piston 206, a metallic head 236 having an inclined ring-like guiding path 238 formed in an outer peripheral surface and a coupling means having a protruding portion engaged with the guiding path 238 and a driving means 240 movable along the guiding path 238 are incorporated, and the piston 206 is reciprocated in an axial direction following its rotational motion.