Disclosed herein is an inertial sensor. The inertial sensor 100 according to preferred embodiments of the present invention includes: a membrane 110; a mass body 120 disposed under the membrane 110; a piezoelectric body 130 formed on the membrane 110 to drive the mass body 120; and trenches 140 formed by being collapsed in a thickness direction of the piezoelectric body 130 so as to vertically meet a direction in which the mass body 120 is driven. By this configuration, the trenches are formed by being collapsed in a thickness direction of the piezoelectric body 130 to provide directivity while retaining the rigidity of the piezoelectric body 130 to prevent a wave from being propagated in an unnecessary direction, thereby driving the inertial sensor 100 in a desired specific direction.