A laundry treatment apparatus comprising: a cabinet forming an appearance of the apparatus; a drum disposed in the cabinet and having a laundry space therein to accommodate laundry; a rotating shaft for rotatably supporting the drum in the cabinet; a balancer (51, 53) comprising: a housing fixed to the drum; an accommodation space defined in the housing; at least two balancing units, each of the balancing units comprising: a unit body movably provided in the accommodation space, wheels adapted to support the unit body, a motor provided in the unit body to rotate the wheels, and unit power lines provided at the unit body to supply power to the motor; and a housing power line provided in the accommodation space to be in contact with the unit power lines to supply electric power to the motor; a shaft through-hole formed through the rotating shaft; a first connecting line (671a, 671b) disposed in the shaft through-hole and connected to a power source; a second connecting line (673a, 673b) connected to the housing power line; and a connector (8, 8a, 8b) for coupling the first connecting line (671a, 671b) to the second connecting line (673a, 673b), characterized by: a control unit configured to detect positions of the balancing units, wherein the housing power line is provided on an inner surface of the accommodating space that is located in a direction to which the unit body is driven by centrifugal force generated by the rotation of the drum, the housing power line has protrusions or grooves that are configured to cause variation in a cross-sectional area of the housing power line, and the control unit is configured to detect the positions of the balancing units by receiving the magnitude of electrical current transmitted by the balancing units when the unit power lines pass the protrusions or grooves. a cabinet forming an appearance of the apparatus; a drum disposed in the cabinet and having a laundry space therein to accommodate laundry; a rotating shaft for rotatably supporting the drum in the cabinet; a balancer (51, 53) comprising: a housing fixed to the drum; an accommodation space defined in the housing; at least two balancing units, each of the balancing units comprising: a unit body movably provided in the accommodation space, wheels adapted to support the unit body, a motor provided in the unit body to rotate the wheels, and unit power lines provided at the unit body to supply power to the motor; and a housing power line provided in the accommodation space to be in contact with the unit power lines to supply electric power to the motor; a housing fixed to the drum; an accommodation space defined in the housing; at least two balancing units, each of the balancing units comprising: a unit body movably provided in the accommodation space, wheels adapted to support the unit body, a motor provided in the unit body to rotate the wheels, and unit power lines provided at the unit body to supply power to the motor; and a housing power line provided in the accommodation space to be in contact with the unit power lines to supply electric power to the motor; a shaft through-hole formed through the rotating shaft; a first connecting line (671a, 671b) disposed in the shaft through-hole and connected to a power source; a second connecting line (673a, 673b) connected to the housing power line; and a connector (8, 8a, 8b) for coupling the first connecting line (671a, 671b) to the second connecting line (673a, 673b), characterized by: a control unit configured to detect positions of the balancing units, wherein the housing power line is provided on an inner surface of the accommodating space that is located in a direction to which the unit body is driven by centrifugal force generated by the rotation of the drum, the housing power line has protrusions or grooves that are configured to cause variation in a cross-sectional area of the housing power line, and the control unit is configured to detect the positions of the balancing units by receiving the magnitude of electrical current transmitted by the balancing units when the unit power lines pass the protrusions or grooves. a control unit configured to detect positions of the balancing units, wherein the housing power line is provided on an inner surface of the accommodating space that is located in a direction to which the unit body is driven by centrifugal force generated by the rotation of the drum, the housing power line has protrusions or grooves that are configured to cause variation in a cross-sectional area of the housing power line, and the control unit is configured to detect the positions of the balancing units by receiving the magnitude of electrical current transmitted by the balancing units when the unit power lines pass the protrusions or grooves. the housing power line is provided on an inner surface of the accommodating space that is located in a direction to which the unit body is driven by centrifugal force generated by the rotation of the drum, the housing power line has protrusions or grooves that are configured to cause variation in a cross-sectional area of the housing power line, and the control unit is configured to detect the positions of the balancing units by receiving the magnitude of electrical current transmitted by the balancing units when the unit power lines pass the protrusions or grooves.