An engine cover (23) is provided between a counterweight (7) and a rear surface part (15B) of a cab (15) to be capable of opening/closing in an upper-lower direction and a heat exchanger cover (28) is provided between the rear side of a left side surface part (15C) and a right side surface part (15D) of the cab (15) and a revolving frame (6). The heat exchanger cover (28) is formed of a horizontal-opening structure of being rotatable in a front-rear direction to the revolving frame (6) with a front end (28C) in the front-rear direction as a fulcrum and a rear end (28D) in the front-rear direction as a free end. A heat exchanger cover lock mechanism (32) is provided on the rear end side of the heat exchanger cover (28) to hold the heat exchanger cover (28) in a closed state, and in a state where both the heat exchanger cover (28) and the engine cover (23) are closed, the engine cover (23) covers the rear end (28D) of the heat exchanger cover (28) and the heat exchanger cover lock mechanism (32) from backward.