An intake air supply construction for an engine, comprising: an intake pipe through which intake air flows; an intake manifold that is connected to the intake pipe so as to induce the intake air into a plurality of intake ports that are aligned in a cylinder head; an intercooler that is incorporated in the intake manifold so as to cool the intake air, wherein the intake manifold includes an inlet that is provided to lie closer to one of two side surfaces that follows an intake air passing direction in the intercooler and intersects an aligning direction of the intake ports, a downstream end portion of the intake pipe in relation to a flowing direction of the intake air is connected to the inlet in a state that an axis center of the downstream end portion is inclined in a direction in which the axis center moves towards the other of the two side surfaces as the axis center extends towards a downstream side of the flow of the intake air, the aligning direction of the intake ports and a passing direction in which the intake air passes through an interior of the inter cooler are set in a horizontal direction, the downstream end portion of the intake pipe is connected to the inlet from a top-bottom direction which is a direction that intersects both the aligning direction of the intake ports and the passing direction of the intercooler, the intake air supply construction further comprising: a butterfly type throttle valve that is incorporated in the downstream end portion of the intake pipe so as to rotate about a shaft portion, characterized in that the shaft portion extends in a direction that follows the intake air passing direction in the intercooler and is at right angles to the port aligning direction, wherein the one of the two side surfaces is situated on a side of one of two flow paths that are divided into two by the throttle valve when the throttle valve is located in an intermediate position, wherein the one of the two flow paths has a flow path area being narrower than that of the other one of the two flow paths at upstream side of the shaft portion. an intake pipe through which intake air flows; an intake manifold that is connected to the intake pipe so as to induce the intake air into a plurality of intake ports that are aligned in a cylinder head; an intercooler that is incorporated in the intake manifold so as to cool the intake air, wherein the intake manifold includes an inlet that is provided to lie closer to one of two side surfaces that follows an intake air passing direction in the intercooler and intersects an aligning direction of the intake ports, a downstream end portion of the intake pipe in relation to a flowing direction of the intake air is connected to the inlet in a state that an axis center of the downstream end portion is inclined in a direction in which the axis center moves towards the other of the two side surfaces as the axis center extends towards a downstream side of the flow of the intake air, the aligning direction of the intake ports and a passing direction in which the intake air passes through an interior of the inter cooler are set in a horizontal direction, the downstream end portion of the intake pipe is connected to the inlet from a top-bottom direction which is a direction that intersects both the aligning direction of the intake ports and the passing direction of the intercooler, the intake air supply construction further comprising: a butterfly type throttle valve that is incorporated in the downstream end portion of the intake pipe so as to rotate about a shaft portion, characterized in that the shaft portion extends in a direction that follows the intake air passing direction in the intercooler and is at right angles to the port aligning direction, wherein the one of the two side surfaces is situated on a side of one of two flow paths that are divided into two by the throttle valve when the throttle valve is located in an intermediate position, wherein the one of the two flow paths has a flow path area being narrower than that of the other one of the two flow paths at upstream side of the shaft portion.