A combustion pressure detection device which detects combustion pressure inside a combustion chamber of an internal combustion engine, the combustion pressure detection device being attachable to a communication hole communicating an inside of a cylinder head configuring the combustion chamber and an outside thereof, the combustion pressure detection device comprising: a housing; and a detector that is located in the housing and detects the combustion pressure, wherein the housing has an attachment structural part (333, 315a) attachable to the communication hole, the attachment structural part (333, 315a) has a first attachment structural part to which a first seal member is attached, and a second attachment structural part to which a second seal member (72; 73; 74) is attached, and the second attachment structural part is provided with a tapered part having a diameter increasing as approaching a rear end side that is an opposite side of a direction to the combustion chamber from a front end side and is arranged at the front end side in the direction to the combustion chamber relative to the first attachment structural part, and the second seal member (72; 73; 74) is attached to the tapered part, the combustion pressure detection device being characterized in that: the first attachment structural part is provided with a face perpendicular to a centerline of the communication hole, and the first seal member is attached onto the face, the detector is arranged inside of the communication hole, and the first seal member is a metal gasket and the second seal member (73, 74) is made of a fluorine resin, wherein, when the pressure detection device is fastened to the cylinder head, the first seal member is attached to and pressed between the cylinder head and the first attachment structural part, and the second seal member (72; 73; 74) is attached to and pressed between the communication hole and the second attachment structural part. a housing; and a detector that is located in the housing and detects the combustion pressure, wherein the housing has an attachment structural part (333, 315a) attachable to the communication hole, the attachment structural part (333, 315a) has a first attachment structural part to which a first seal member is attached, and a second attachment structural part to which a second seal member (72; 73; 74) is attached, and the second attachment structural part is provided with a tapered part having a diameter increasing as approaching a rear end side that is an opposite side of a direction to the combustion chamber from a front end side and is arranged at the front end side in the direction to the combustion chamber relative to the first attachment structural part, and the second seal member (72; 73; 74) is attached to the tapered part, the combustion pressure detection device being characterized in that: the first attachment structural part is provided with a face perpendicular to a centerline of the communication hole, and the first seal member is attached onto the face, the detector is arranged inside of the communication hole, and the first seal member is a metal gasket and the second seal member (73, 74) is made of a fluorine resin, wherein, when the pressure detection device is fastened to the cylinder head, the first seal member is attached to and pressed between the cylinder head and the first attachment structural part, and the second seal member (72; 73; 74) is attached to and pressed between the communication hole and the second attachment structural part. the first attachment structural part is provided with a face perpendicular to a centerline of the communication hole, and the first seal member is attached onto the face, the detector is arranged inside of the communication hole, and the first seal member is a metal gasket and the second seal member (73, 74) is made of a fluorine resin, wherein, when the pressure detection device is fastened to the cylinder head, the first seal member is attached to and pressed between the cylinder head and the first attachment structural part, and the second seal member (72; 73; 74) is attached to and pressed between the communication hole and the second attachment structural part.