A multi-axis accelerometer or a multi-axis angular rate sensor which can be made by an easy process and the size of which can be greatly reduced is provided. An inertia sensor has a substrate, a flat proofmass formed on the substrate and a stacked structure including at least a lower electrode, a piezoelectric film, and an upper electrode, an anchor unit formed in a cutout inside of the proofmass and fixed on the substrate, and a plurality of flat piezoelectric beams each having one end connected to the proofmass, the other end connected to the anchor unit, and a stacked structure formed in a cutout inside of the proofmass and including at least a lower electrode, a piezoelectric film, and an upper electrode, wherein the inertia sensor enables to detect an acceleration applied on the proofmass based on charges generated to the electrodes of the piezoelectric beams.