A combustion pressure detection device for detecting 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 includes: a housing; and an piezoelectric element and the like that are located in the housing and detect the combustion pressure. The housing has an attachment structural part attachable to the communication hole, the attachment structural part has a third outer peripheral surface to which a first seal member is attachable, and a inclined surface to which a second seal member is attachable, and the inclined surface is arranged at a front end side in a direction to the combustion chamber relative to the third outer peripheral surface when the combustion pressure detection device is attached to the communication hole.