Disclosed herein is an inertial sensor of the present invention. An inertial sensor 100 according to a preferred embodiment of the present invention includes a plate-shaped membrane 110, a mass body 120 disposed under a central portion 113 of the membrane 110, a post 130 disposed under an edge 115 of the membrane 110 and surrounding the mass body 120, a piezoelectric material 140 formed above the membrane 110 and provided with a cavity 141 in a thickness direction, a sensing electrode 150 disposed in the cavity 141 and a driving electrode 160 disposed outside the cavity 141, whereby the thickness of the piezoelectric material 140 of the portion on which the sensing electrode 150 is disposed is formed to be thin, such that the sensitivity of the inertial sensor 100 can be improved.