To remove a combustion product contained in a burnt gas more efficiently while suppressing an increase in the part count and pressure loss to a minimum in a working gas circulation type engine.

In the working gas circulation type engine having a condensation means interposed in a circulation passage to re-supply the burnt gas discharged from a combustion chamber to the combustion chamber, the temperature of the circulation passage in the upstream side of the condensation means and the burnt gas flowing in the circulation passage is lowered by arranging a heat pipe between the circulation passage in the upstream side and the circulation passage in the down stream side in the condensation means and as a result, the quantity of the vapor of the combustion product contained in the burnt gas re-supplied to the combustion chamber is further reduced.