To provide a chemicals feed pump which is free from the unnatural deformation of a flexible film, and has high durability, and in which the change of the delivery amount with the lapse of time, can be reduced.

The pump chamber 1 of a chemicals feed pump 10 comprises an almost cylindrical flexible film 2, an outflow side fixing member having a chemicals flowing hole 3a, and an inflow side fixing member 4 having a chemicals inflow port 4a. The chemicals R are supplied to the pump chambers through a chemicals bottle 21, an inflow side piping 22, and a check valve 11. A nodal flexible film 2 is surrounded by the pure water non-compressive fluid 6 filled inside of the pressure chamber 5, and the pure water is poured and sucked out to the pressure chamber 6 by an actuator 40 and a piping 42. The inflow side fixing member 4 is arranged deformably in a vertical direction corresponding to the deformation of the flexible film at that time, and a chemicals inflow tube 7 formed from the chemicals inflow port 4a of a pressure chamber chemicals inflow part 5e formed on a wall face 5d of the pressure chamber 5, comprises a coiled part 7a of a redundant length for permitting the deformation of the inflow side fixing member 4.