A drum type washing machine, comprising: a housing; a spin tub to hold laundry to be washed; and a ball balancer (20,30) coupled to the spin tub to compensate for a dynamic imbalance during rotation thereof, the ball balancer (20,30) comprising a first housing (22, 32) and a second housing (23,33) joined to each other to form an annular-shaped race having a closed internal space in which a plurality of balls and viscous fluid are accommodated, the first housing (22,32) including a first side wall (22a,32a), a second side wall (22b,32b) and a connecting wall (22c,32c) to form a three-sided annular-shaped structure having an open side, and the second housing (23,33) being adapted to cover the open side of the first housing (22,32), the first housing (22, 32) having at least one support (24, 34) for reinforcing a strength of the balancer (20, 30), characterized in that the spin tub is rotating with respect to a substantially horizontal axis of the drum type washing machine, a front member is attached to a front end of the spin tub, wherein said front member is provided with at least one annular recess corresponding to the balancer (20, 30) such that the balancer (20, 30) is able to be coupled to the spin tub by being fitted within the recess, and the front member having a front wall with an opening formed therein for receiving laundry, wherein an outer annular side wall of the recess establishing physical contact with a predefined area of an inner surface of the spin tub, wherein the support (24, 34) protrudes from the first housing (22, 32) and comes into contact with the outer annular side wall of the recess, and guides the balancer (20, 20) to be maintained in the recess in place. a housing; a spin tub to hold laundry to be washed; and a ball balancer (20,30) coupled to the spin tub to compensate for a dynamic imbalance during rotation thereof, the ball balancer (20,30) comprising a first housing (22, 32) and a second housing (23,33) joined to each other to form an annular-shaped race having a closed internal space in which a plurality of balls and viscous fluid are accommodated, the first housing (22,32) including a first side wall (22a,32a), a second side wall (22b,32b) and a connecting wall (22c,32c) to form a three-sided annular-shaped structure having an open side, and the second housing (23,33) being adapted to cover the open side of the first housing (22,32), the first housing (22, 32) having at least one support (24, 34) for reinforcing a strength of the balancer (20, 30), characterized in that the spin tub is rotating with respect to a substantially horizontal axis of the drum type washing machine, a front member is attached to a front end of the spin tub, wherein said front member is provided with at least one annular recess corresponding to the balancer (20, 30) such that the balancer (20, 30) is able to be coupled to the spin tub by being fitted within the recess, and the front member having a front wall with an opening formed therein for receiving laundry, wherein an outer annular side wall of the recess establishing physical contact with a predefined area of an inner surface of the spin tub, wherein the support (24, 34) protrudes from the first housing (22, 32) and comes into contact with the outer annular side wall of the recess, and guides the balancer (20, 20) to be maintained in the recess in place.