To obtain long-period stable continuation of a seal function in a plunger pump part and eliminate a pulsation feed generated, when a piston is advanced/retracted, in a parallel feed pump device mounted in a two-liquid mixed feed line simultaneously feeding, two liquids by prescribed ratio feed supplied from a mixed supply part in a line end.

A two-liquid parallel feed pump device 1 comprises a lateral one series integral single cylinder unit 10 of three-room divided structure by arranging A-agent/B-agent plunger pump parts 2, 3 in series on both sides of hydraulic drive part 4, internally provides a single piston rod 6 having a piston 5 respectively in the three rooms inside this cylinder unit 10, provides a lubricant pool part 16 wrapping the outer periphery of the piston rod 6 penetrating a partition 9 dividing the three rooms, and has a piston rod form and a feed agent pipe constitution where the A/B-agent plunger pump parts 2, 3 transfer pools 1/2 extrusion amount by advancing of the piston 5 in the respective piston rear room 13 to feed the rest of 1/2 to a mixed supply part 24.