Disclosed herein is an inertial sensor including: a membrane; a mass body provided under the membrane; a plurality of patterned magnets provided under the mass body; and a magnetoresistive element provided to be spaced apart from the mass body and measuring static DC acceleration acting on the mass body through resistance changed according to magnetic fields of the plurality of patterned magnets. The plurality of patterned magnets and the magnetoresistive element are included, thereby making it possible to measure static DC acceleration (particularly, gravity acceleration) that is difficult to measure using an existing to piezoelectric element.