PURPOSE: To prevent occurrence of pulsation of fluid flow due to backflow of fluid to be conveyed, by making rollers travel along a guide plate having a contour constituted by straight sections and arcuate sections connected to each other, and detaching the rollers away from a tube gradually along the straight contour section of the guide plate on the discharge side of the pump.

CONSTITUTION: Since arrangement is such that the travelling speed of rollers 3 at straight sections 6b of a guide plate 6 is lower than that at an arcuate section 6al, the pressure of fluid in a tube 2 between a preceding roller 3-1 and a succeeding roller 3-2 is increased by the above difference of the travelling speed of the rollers before the tube 2 is opened, so that backflow of high-pressure fluid on the discharge side into the tube 2, due to the rising of fluid pressure on the discharge side at the time of discharging fluid, can be prevented. At the same time, it is prevented that the amount of fluid equal to the volume of the tube 2 confined between the above two rollers flows back into the tube 2 when the rollers 3 are detached gradually away from the tube 2. Thus, it is enabled to prevent occurrence of pulsation of the discharged fluid.