A drum type washing machine including a housing, a rotating spin tub to hold laundry to be washed and a ball balancer coupled to the spin tub to compensate for a dynamic imbalance during rotation thereof. The ball balancer includes a first plastic member and a second plastic member joined to each other to form a closed internal space in which a plurality of balls and viscous fluid are accommodated, the first plastic member includes a first side wall, a second side wall and a connecting wall to form a three-sided annular-shaped structure having an open side, and the second plastic member is adapted to cover the open side of the first plastic member. A diameter of each of the balls is smaller than a depth of the three-sided annular-shaped structure measured from the connecting wall to a top of the first side wall.