To provide a portable sterilization device capable of easily sterilizing a used toothbrush anywhere.

This device is provided with a freely openable and closable lid member 2 attached to the upper surface of a main body case 1, a tray 10 attachably and detachably provided inside the main body case 1 for housing the toothbrush 8, an ultraviolet ray sterilization lamp 3 for irradiating the brush part 8a of the toothbrush 8 with ultraviolet rays and a detection switch for detecting that the lid member 2 is closed. Then, a housing recessed part similar to the shape of the toothbrush 8 is formed at the tray 10 and an opening part 13 is formed at a position corresponding to the brush part 8a in the housing recessed part.