An apparatus for removing contaminants of working fluid of a construction machine is provided to filter the contaminants by a second filter element even through the contaminants are bypassed without being filtered by a first filter element. An apparatus(1) for removing contaminants of working fluid of a construction machine comprises as the follows. A hydraulic tank is connected to both ends of a working fluid circulation line(10) to circulate working fluid along the working fluid circulation line. A first filter element(20) is installed on the working fluid circulation line to filter contaminants included in the working fluid. Both ends of a first bypass line(30) are connected to the working fluid circulation line located at an inlet and an outlet of the first filter element. A filter protection bypass valve(40) is installed on the first bypass line and opened when a pressure difference between the inlet and the outlet of the first filter element reaches a predetermined value. Both ends of a pressure switch(50) are connected to the working fluid circulation line located at the inlet and the outlet of the first filter element to sense the pressure difference between the inlet and the outlet of the first filter element. An indicator(60) is connected to the pressure switch and informs a user of a replacement time of the first filter element before the pressure difference between the inlet and the outlet of the first filter element reaches the predetermined value.
