A construction machine comprising: an automotive vehicle body (2, 4); an engine mounted on said vehicle body (2, 4) and electronically controlled by a control device; an exhaust gas purifying device provided on an exhaust side of said engine and purifying an exhaust gas; a hydraulic pump of a variable displacement type driven by said engine and subjected to constant torque control so that a product of a delivery pressure and a delivery flow rate becomes constant; and a hydraulic actuator driven by a pressurized oil delivered from said hydraulic pump, when said engine is at a first rotational speed (Ns), a maximum torque (Tm) at a normal operation is outputted, as an engine rotational speed becomes higher than the first rotational speed (Ns), the output torque (Te) becomes smaller, and said engine outputs a rated torque (Tr) at a rated rotational speed (Nm) which is the highest rotational speed at the normal operation, and said control device includes: malfunction determining unit configured to determine whether or not said engine and/or exhaust gas purifying device has a malfunction; and characterized in that in case the malfunction is determined by the malfunction determining unit, engine limiting unit configured to limit a highest rotational speed of said engine to a second rotational speed (Nt) higher by a predetermined amount (α) than a first rotational speed (Ns) at which an engine maximum torque (Tm) before the malfunction can be outputted and for limiting a maximum fuel injection quantity of said engine such that a rated torque (Tr) before the malfunction can be outputted at said first rotational speed (Ns), wherein said predetermined amount (α) is set to a value in accordance with a temporary drop of the rotational speed caused by addition of a peak torque of said hydraulic pump to said engine. an automotive vehicle body (2, 4); an engine mounted on said vehicle body (2, 4) and electronically controlled by a control device; an exhaust gas purifying device provided on an exhaust side of said engine and purifying an exhaust gas; a hydraulic pump of a variable displacement type driven by said engine and subjected to constant torque control so that a product of a delivery pressure and a delivery flow rate becomes constant; and a hydraulic actuator driven by a pressurized oil delivered from said hydraulic pump, when said engine is at a first rotational speed (Ns), a maximum torque (Tm) at a normal operation is outputted, as an engine rotational speed becomes higher than the first rotational speed (Ns), the output torque (Te) becomes smaller, and said engine outputs a rated torque (Tr) at a rated rotational speed (Nm) which is the highest rotational speed at the normal operation, and said control device includes: malfunction determining unit configured to determine whether or not said engine and/or exhaust gas purifying device has a malfunction; and characterized in that in case the malfunction is determined by the malfunction determining unit, engine limiting unit configured to limit a highest rotational speed of said engine to a second rotational speed (Nt) higher by a predetermined amount (α) than a first rotational speed (Ns) at which an engine maximum torque (Tm) before the malfunction can be outputted and for limiting a maximum fuel injection quantity of said engine such that a rated torque (Tr) before the malfunction can be outputted at said first rotational speed (Ns), wherein said predetermined amount (α) is set to a value in accordance with a temporary drop of the rotational speed caused by addition of a peak torque of said hydraulic pump to said engine.