Construction Machine

Provided is a construction machine that can prevent a machine body from being lowered since a blade is not put into a float state even where a misoperation is made by an operator when the machine body is in a jacked-up state, and that can perform a favorable leveling operation by putting the blade into the float state in accordance with an operator's operation when the machine body is not in the jacked-up state. A hydraulic excavator includes a controller 42 that determines whether or not the machine body is in a jacked-up state and controls a float valve 41. In the case where it is determined that the machine body is not in the jacked-up state, the controller 42 changes over the float valve 41 to a float position V and invalidates an operation of a blade control valve 22, in accordance with a float instruction. In the case where it is determined that the machine body is in the jacked-up state, the controller 42 holds the float valve 41 in a reference position IV and validates the operation of the blade control valve 22, irrespectively of the presence or absence of the float instruction.