An engine comprising: a cylinder block having a cylinder ; a cylinder head attached to the cylinder block , the cylinder head having an exhaust port communicating with the interior of the cylinder ; and a catalyst storage case attached to the cylinder head , wherein the catalyst storage case comprises: a case body having an inlet , an outlet , and an exhaust passage extending from the inlet to the outlet for allowing exhaust gas to pass therethrough; and a plurality of oxidation catalysts (61;62) disposed in the exhaust passage of the case body , wherein the plurality of oxidation catalysts are arrayed in a direction intersecting a direction along which the exhaust passage extends; wherein the inlet of the catalyst storage case is in communication with the exhaust port of the cylinder head ; the cylinder block has a piston disposed in the cylinder and a crankshaft coupled to the piston , the cylinder block has a load-side end face from which a load-side end of the crankshaft protrudes, wherein the engine is characterized in that : the catalyst storage case is disposed toward the load-side end face of the cylinder block , and the longitudinal axes of the plurality of oxidation catalysts (61;62) in the catalyst storage case are in a plane orthogonal to the axis of the shaft center (L) of the crankshaft . a cylinder block having a cylinder ; a cylinder head attached to the cylinder block , the cylinder head having an exhaust port communicating with the interior of the cylinder ; and a catalyst storage case attached to the cylinder head , wherein the catalyst storage case comprises: a case body having an inlet , an outlet , and an exhaust passage extending from the inlet to the outlet for allowing exhaust gas to pass therethrough; and a plurality of oxidation catalysts (61;62) disposed in the exhaust passage of the case body , wherein the plurality of oxidation catalysts are arrayed in a direction intersecting a direction along which the exhaust passage extends; wherein a case body having an inlet , an outlet , and an exhaust passage extending from the inlet to the outlet for allowing exhaust gas to pass therethrough; and a plurality of oxidation catalysts (61;62) disposed in the exhaust passage of the case body , wherein the plurality of oxidation catalysts are arrayed in a direction intersecting a direction along which the exhaust passage extends; wherein the inlet of the catalyst storage case is in communication with the exhaust port of the cylinder head ; the cylinder block has a piston disposed in the cylinder and a crankshaft coupled to the piston , the cylinder block has a load-side end face from which a load-side end of the crankshaft protrudes, wherein the engine is characterized in that : the catalyst storage case is disposed toward the load-side end face of the cylinder block , and the longitudinal axes of the plurality of oxidation catalysts (61;62) in the catalyst storage case are in a plane orthogonal to the axis of the shaft center (L) of the crankshaft . the catalyst storage case is disposed toward the load-side end face of the cylinder block , and the longitudinal axes of the plurality of oxidation catalysts (61;62) in the catalyst storage case are in a plane orthogonal to the axis of the shaft center (L) of the crankshaft . <EOS>