Provided is a beta voltaic battery including a first semiconductor layer, a second semiconductor layer, and a beta-ray generator which is disposed between the first semiconductor layer and the second semiconductor layer and includes a metal substrate having both sides coated with a radioisotope layer. The beta voltaic battery according to the present invention has no sealing layer, but may efficiently shield beta rays through a sandwich structure. Since the sealing layer is absent, the absorption of beta rays by the semiconductor may be improved, and excellent energy conversion efficiency may be obtained because output is improved due to the two semiconductor layers and the radioisotope ray source coated on the both sides.