A luminaire comprising: a luminaire main body that includes an abutment portion in which heat is transferred and a mounting receiving portion; a socket device that includes a socket main body having a lower surface formed in the shape of a plane, and a cylindrical portion having a predetermined thickness and height provided on an upper surface, wherein the cylindrical portion is formed so as to include an opening portion in a center region of the lower surface, an engagement receiving portion which is provided in the opening portion, a screw which is fixed to the mounting receiving portion, a receiving portion which receives an elastic member generating an elastic force between the socket main body and the screw, and a connection portion (20, 21, 28) which is electrically connected to an external power source, wherein the socket device is mounted on the luminaire main body so as to move in an elasticity direction of the elastic member with respect to the luminaire main body by the screw; and a lamp device that includes a contact portion which contacts the abutment portion, an engagement portion which engages with the engagement receiving portion, and a lamp side connection portion which is electrically connected to the connection portion (20, 21, 28), wherein the abutment portion of the luminaire main body and the contact portion of the lamp device closely contact with each other by the elastic force of the elastic member according to an operation in which the engagement portion of the lamp device and the engagement receiving portion of the socket device are engaged with each other, characterized in that the screw comprises a screwed portion, an intermediate portion and a head portion in which the diameter of the intermediate portion is smaller than that of the head portion and is larger than that of the screwed portion, the intermediate portion is formed in a size which can be inserted into a small diameter portion of a penetrating hole which is formed in the receiving portion, the screwed portion is formed so as to be screwed to the mounting receiving portion, the head portion is screwed to the luminaire main body so as not to protrude from the lower surface of the socket main body in a state where the mounting position of the screw to the luminaire main body is regulated by the intermediate portion, and the elastic member generates the elastic force between a step portion of the receiving portion of the socket main body and the head portion of the screw, thereby pressing the receiving portion to the luminaire main body side, and the upper surface of the receiving portion is formed so as to abut the inner surface of the abutment portion of the luminaire main body. a luminaire main body that includes an abutment portion in which heat is transferred and a mounting receiving portion; a socket device that includes a socket main body having a lower surface formed in the shape of a plane, and a cylindrical portion having a predetermined thickness and height provided on an upper surface, wherein the cylindrical portion is formed so as to include an opening portion in a center region of the lower surface, an engagement receiving portion which is provided in the opening portion, a screw which is fixed to the mounting receiving portion, a receiving portion which receives an elastic member generating an elastic force between the socket main body and the screw, and a connection portion (20, 21, 28) which is electrically connected to an external power source, wherein the socket device is mounted on the luminaire main body so as to move in an elasticity direction of the elastic member with respect to the luminaire main body by the screw; and a lamp device that includes a contact portion which contacts the abutment portion, an engagement portion which engages with the engagement receiving portion, and a lamp side connection portion which is electrically connected to the connection portion (20, 21, 28), wherein the abutment portion of the luminaire main body and the contact portion of the lamp device closely contact with each other by the elastic force of the elastic member according to an operation in which the engagement portion of the lamp device and the engagement receiving portion of the socket device are engaged with each other,