PURPOSE: To provide a mechanical quantity sensor which can be manufactured easily and can detect mechanical quantities simultaneously in the direction normal to a substrate and in the direction in parallel with the substrate.

CONSTITUTION: A V-valley is made in a substrate 31 with electrodes 33, 35 being provided on the banks thereof and a beam structure 37 having profile corresponding to that of the V-valley is mounted on the substrate 31. Upon application of mechanical quantity from the outside, the beam structure 37 displaces regardless of the applying direction of mechanical quantity thus varying the capacitances between the beam structure 37 and the electrodes 33, 35. Magnitude of mechanical quantity can be determined basing on the variation of the capacitances.