A cab for a construction machine, comprising: a cab body defining an operator's compartment and including a front window member facing forward; a guard for protecting the cab body; and a wiper configured to wipe off water droplets on an outer surface of the front window member, wherein: the wiper includes a pair of link arms having respective proximal ends, a blade supported by the pair of link arms so as to make tight contact with an outer surface of the front window member, and a blade actuator configured to swing the pair of link arms about axes passing through the respective proximal ends of the pair of link arms in a front-rear direction to thereby reciprocate the blade along the outer surface of the front window member; the blade actuator includes a link arm support unit (331, 334) that supports the respective proximal ends of the pair of link arms so as to allow the pair of link arms to swing, a blade drive motor for generating power, and a drive transmission mechanism configured to transmit the power generated by the blade drive motor to the pair of link arms to swing the pair of link arms; and the guard includes a pair of side pillars extending along opposite edges of the cab body in a width direction of the cab body, respectively, and at least one beam (12A, 12B, 12C, 12D) disposed between the pair of side pillars to interconnect the pair of side pillars in the width direction, characterized in that the at least one beam (12A, 12B, 12C, 12D) includes an actuator housing beam that houses the blade actuator, the actuator housing beam including a hollow beam body extending in the width direction along an upper front portion of the cab body, and a front-rear partition plate partitioning a beam interior space, which is an internal space of the beam body, into front and rear sections; and the beam body is formed with a body opening (212, 213) that provides communication between an inside and an outside of the beam body, the body opening (212, 213) allowing the blade actuator to be assembled to the front-rear partition plate through the body opening (212, 213) and allowing the pair of link arms to extend from the blade actuator to the outside of the actuator housing beam through the body opening (212, 213) to support the blade. a cab body defining an operator's compartment and including a front window member facing forward; a guard for protecting the cab body; and a wiper configured to wipe off water droplets on an outer surface of the front window member, wherein: the wiper includes a pair of link arms having respective proximal ends, a blade supported by the pair of link arms so as to make tight contact with an outer surface of the front window member, and a blade actuator configured to swing the pair of link arms about axes passing through the respective proximal ends of the pair of link arms in a front-rear direction to thereby reciprocate the blade along the outer surface of the front window member; the blade actuator includes a link arm support unit (331, 334) that supports the respective proximal ends of the pair of link arms so as to allow the pair of link arms to swing, a blade drive motor for generating power, and a drive transmission mechanism configured to transmit the power generated by the blade drive motor to the pair of link arms to swing the pair of link arms; and the guard includes a pair of side pillars extending along opposite edges of the cab body in a width direction of the cab body, respectively, and at least one beam (12A, 12B, 12C, 12D) disposed between the pair of side pillars to interconnect the pair of side pillars in the width direction, the wiper includes a pair of link arms having respective proximal ends, a blade supported by the pair of link arms so as to make tight contact with an outer surface of the front window member, and a blade actuator configured to swing the pair of link arms about axes passing through the respective proximal ends of the pair of link arms in a front-rear direction to thereby reciprocate the blade along the outer surface of the front window member; the blade actuator includes a link arm support unit (331, 334) that supports the respective proximal ends of the pair of link arms so as to allow the pair of link arms to swing, a blade drive motor for generating power, and a drive transmission mechanism configured to transmit the power generated by the blade drive motor to the pair of link arms to swing the pair of link arms; and the guard includes a pair of side pillars extending along opposite edges of the cab body in a width direction of the cab body, respectively, and at least one beam (12A, 12B, 12C, 12D) disposed between the pair of side pillars to interconnect the pair of side pillars in the width direction, characterized in that the at least one beam (12A, 12B, 12C, 12D) includes an actuator housing beam that houses the blade actuator, the actuator housing beam including a hollow beam body extending in the width direction along an upper front portion of the cab body, and a front-rear partition plate partitioning a beam interior space, which is an internal space of the beam body, into front and rear sections; and the beam body is formed with a body opening (212, 213) that provides communication between an inside and an outside of the beam body, the body opening (212, 213) allowing the blade actuator to be assembled to the front-rear partition plate through the body opening (212, 213) and allowing the pair of link arms to extend from the blade actuator to the outside of the actuator housing beam through the body opening (212, 213) to support the blade.