The invention relates to a method for measuring pressure in an underground formation containing a fluid, comprising the following consecutive steps: establishing fluid communication between a test chamber arranged in a drilling well and the underground formation, via a flowline; moving a piston in the test chamber so as to suction fluid into the test chamber; ensuring fluid isolation of the test chamber relative to the flowline; measuring the pressure in the flowline; and repeating the preceding steps. The invention also relates to a device for measuring pressure in an underground formation containing a fluid adapted for the implementation of said method.