Disclosed herein is an inertial sensor, which includes a diaphragm having a piezoelectric element or a piezoresistive element formed on one surface thereof, a mass element integrated with the center of the other surface of the diaphragm in which the distal end of the mass element has a larger width than the width of the proximal end in contact with the diaphragm, and a supporter formed along the edge of the other surface of the diaphragm, so that the use of the mass element having the above shape results in decreased spring constant and increased distance from the center of the diaphragm to the center of the mass element, thereby simultaneously realizing a reduction in the size of the inertial sensor and an increase in performance thereof. A method of manufacturing the inertial sensor is also provided.