A washing machine comprising: a washing tub; and a water transmission device configured to discharge water of the washing tub, the water transmission device including: a filter case disposed under the washing tub, the filter case accommodating a filter, and the filter case accepting the water from the washing tub; a pump case connected to the filter case, the pump case accommodating an impeller, the impeller configured to suction the water in the filter case and discharge; a motor configured to rotate the impeller; a suction hole communicating a side portion of the pump case facing a center of the impeller with a side portion of the filter case; a water discharge pipeline formed under the pump case; and an outlet opened downward from a lowest end inside the pump case, the outlet communicating with the water discharge pipeline, wherein an upper region inside the filter! case communicates with an interior of the pump case through the suction hole, characterized in that the washing machine further comprises one or more communicating paths provided under the suction hole, the one or more communicating paths communicating a lower region inside the filter case with the outlet. a washing tub; and a water transmission device configured to discharge water of the washing tub, the water transmission device including: a filter case disposed under the washing tub, the filter case accommodating a filter, and the filter case accepting the water from the washing tub; a pump case connected to the filter case, the pump case accommodating an impeller, the impeller configured to suction the water in the filter case and discharge; a motor configured to rotate the impeller; a suction hole communicating a side portion of the pump case facing a center of the impeller with a side portion of the filter case; a water discharge pipeline formed under the pump case; and an outlet opened downward from a lowest end inside the pump case, the outlet communicating with the water discharge pipeline, wherein an upper region inside the filter! case communicates with an interior of the pump case through the suction hole, characterized in that the washing machine further comprises one or more communicating paths provided under the suction hole, the one or more communicating paths communicating a lower region inside the filter case with the outlet. a filter case disposed under the washing tub, the filter case accommodating a filter, and the filter case accepting the water from the washing tub; a pump case connected to the filter case, the pump case accommodating an impeller, the impeller configured to suction the water in the filter case and discharge; a motor configured to rotate the impeller; a suction hole communicating a side portion of the pump case facing a center of the impeller with a side portion of the filter case; a water discharge pipeline formed under the pump case; and an outlet opened downward from a lowest end inside the pump case, the outlet communicating with the water discharge pipeline, wherein an upper region inside the filter! case communicates with an interior of the pump case through the suction hole, characterized in that the washing machine further comprises one or more communicating paths provided under the suction hole, the one or more communicating paths communicating a lower region inside the filter case with the outlet.