A combined heat and smoke detector, comprising: a housing comprised of a body base and a body case covering an entire upper side of the body base; a circuit substrate mounted on a top surface of the body base and disposed inside the housing; a smoke detecting portion configured to detect smoke flowing into a dark chamber and disposed inside the housing; and a plurality of heat detecting means for detecting heat, the plurality of heat detecting means disposed inside the housing, the plurality of heat detecting means are arranged lateral to the dark chamber, characterized in that a shield case is mounted on the body base, the shield case covering an entire top surface of the circuit substrate; and an extension portion integrally formed with the dark chamber, the extension portion laterally extending from a bottom end of the dark chamber, wherein one of the heat detecting means is upwardly projected to be inserted into a penetration hole portion formed in the shield case and an inserted portion formed in the extension portion, wherein the dark chamber is mounted on the shield case by rotation of the dark chamber relative to the shield case in a state where the one of the heat detecting means is inserted into the inserted portion, wherein the inserted portion has such a shape that one portion (9a1) thereof, into which the one of the heat detecting means is inserted after the rotation and the other portion (9a2) thereof, into which the one of the heat detecting means is inserted prior to the rotation are continued to each other, wherein the one portion (9a1) into which the one of the heat detecting means is inserted after the rotation is narrower than the other portion (9a2) into which the one of the heat detecting means is inserted prior to the rotation, and wherein the penetration hole portion is wider than the one portion (9a1) into which the one of the heat detecting means is inserted after the rotation. a housing comprised of a body base and a body case covering an entire upper side of the body base; a circuit substrate mounted on a top surface of the body base and disposed inside the housing; a smoke detecting portion configured to detect smoke flowing into a dark chamber and disposed inside the housing; and a plurality of heat detecting means for detecting heat, the plurality of heat detecting means disposed inside the housing, the plurality of heat detecting means are arranged lateral to the dark chamber, characterized in that a shield case is mounted on the body base, the shield case covering an entire top surface of the circuit substrate; and an extension portion integrally formed with the dark chamber, the extension portion laterally extending from a bottom end of the dark chamber, wherein one of the heat detecting means is upwardly projected to be inserted into a penetration hole portion formed in the shield case and an inserted portion formed in the extension portion, wherein the dark chamber is mounted on the shield case by rotation of the dark chamber relative to the shield case in a state where the one of the heat detecting means is inserted into the inserted portion, wherein the inserted portion has such a shape that one portion (9a1) thereof, into which the one of the heat detecting means is inserted after the rotation and the other portion (9a2) thereof, into which the one of the heat detecting means is inserted prior to the rotation are continued to each other, wherein the one portion (9a1) into which the one of the heat detecting means is inserted after the rotation is narrower than the other portion (9a2) into which the one of the heat detecting means is inserted prior to the rotation, and wherein the penetration hole portion is wider than the one portion (9a1) into which the one of the heat detecting means is inserted after the rotation.