To provide a pump reducing the number of part items, having a simple structure, being excellent in maintenability and capable of pumping up a high viscous agent without using a thinner cup.

This pump for the high viscous agent for sucking up the high viscous agent such as an adhesive and a calking agent filled in a vessel from an upper surface of the vessel, comprises a first cylinder 20 for internally installing a piston 10 for reciprocating by driving force supplied from a driving source, a second cylinder 21 being connected to the first cylinder 20 and having the inside put under positive pressure or negative pressure by reciprocating motion of the piston 10, a diaphragm structure having a diaphragm 31 for deviating by pressure in the second cylinder 21 and a third cylinder 40 continuously arranged on the anti-piston 10 side of the second cylinder 21, connected to a vessel upper surface filled with the high viscous agent and provided with a discharge port 60 for externally discharging the high viscous agent sucked by motion of the diaphragm 31.