A lighting apparatus includes a lighting tube 10, a socket 20 and an adapter casing 30. The lighting tube 10 has a lighting tube main body 11, a seating portion 12 provided at a basal end portion of the lighting tube main body, electrode terminals 14 provided at the seating portion, and a connecting portion cover 40 covering a connecting portion formed between the lighting tube main body and the seating portion in a hermetically sealed manner. The adaptor casing 30 and the connecting portion cover 40 are detachably connected in a state in which the socket 20 into which the seating portion 12 of the lighting tube 10 is inserted is accommodated in the socket accommodation space 31, whereby the socket 20 and the seating portion 12 of the lighting tube 10 are hermetically sealed by the adaptor casing 30 and the connecting portion cover 40.