Disclosed herein is an inertial sensor. An inertial sensor 100 according to a preferred embodiment of the present invention includes a plate-shaped membrane 110, a mass body 130 that is provided under a central portion 111 of the membrane 110 and includes an integrated circuit, and a post 140 that are provided under an edge 112 of the membrane 110 to surround the mass body 130, whereby the overall thickness and area of the inertial sensor can be reduced by including the integrated circuit in the mass body 130 to implement a thin and small inertial sensor 100.