A hydraulic oil filtration apparatus 40 comprises an actuation control valve V, a pump-pressure oil passage 41, a connection oil passage 43, a tank oil passage 51, a return filter 60, a drain oil passage 53, a drain filter 70 and an aspirator structure 90. The actuation control valve V controls to charge and discharge a hydraulic actuator A such as a boom cylinder 22 and travel motors with hydraulic oil from a hydraulic pump P, which is connected through the pump-pressure oil passage 41 to the actuation control valve V The hydraulic actuator A is connected with the actuation control valve V by the connection oil passage 43, and the actuation control valve V is connected to a tank T by the tank oil passage 51, in which the return filter 60 is provided. The part of the tank oil passage 51 downstream with respect to the return filter 60 is connected to the hydraulic pump P by the drain oil passage 53, in which the drain filter 70 is provided. The aspirator structure 90 is positioned at the junction between the tank oil passage 51 and the drain oil passage 53, so that leakage oil in the drain oil passage 53 is drawn by the flow of the discharged oil through the tank oil passage 51 and led to the drain filter 70.