Disclosed is a seat pumping device for a vehicle, the seat pumping device including: a clutch drum turned by receiving torque of a lever and having a plurality of compressing protrusions radially formed along an edge thereof to be spaced apart from each other; a brake drum coupled to the clutch drum and having a circular vertical flange protruding toward the clutch drum, the vertical flange having a plurality of supporting protrusions protruding laterally of the vertical flange to be arranged between the compressing protrusions; and a securing portion provided between the vertical flange and the clutch drum which face each other, the securing portion guiding a relative turning of the clutch drum and the brake drum while blocking a relative translation of the clutch drum and the brake drum.