An electromagnetic wave detector is provided. The electromagnetic wave detector comprises: a base; a sensor element arranged on a principal surface of the base and configured to convert, into an electrical signal, light emitted from a scintillator which receives an electromagnetic wave; a lens portion arranged between the scintillator and the sensor element and configured to collect the light generated by the scintillator to the sensor element; a light transmissive portion arranged between the lens portion and the sensor element and configured to transmit the light generated by the scintillator; and a shielding portion including an inner wall located on a periphery of the sensor element and configured to shield the electromagnetic wave. The inner wall is arranged between the light transmissive portion and the principal surface.