A control method of a laundry treating apparatus comprising a tub defining a predetermined space for storing water and having a tub opening formed in a front surface; a drum rotatably provided in the tub and configured to hold laundry; and a sensing unit configured to sense three-shaft acceleration and three-angle angle velocity, the control method comprising: a maintaining step for rotating the drum at a reference rotational speed that is set to be a lower or a higher rotation than a rotational speed causing resonance in the laundry treating apparatus; a measuring step for controlling the sensing unit to measure the maximum displacement (Yf) of a tub front surface, the maximum displacement (Yr) of a tub rear surface and a phase difference (θ) between the maximum displacements (Yf, Yr) during the rotation of the drum at the reference rotational speed; a determining step (S50, S60) for determining a front UB mass (mf) located in a drum front area, a rear UB mass (mr) located in a drum rear area and an angle between the UB masses based on the maximum displacement (Yf) of the tub front surface, the maximum displacement (Yr) of the tub rear surface and the phase difference (θ) between the maximum displacements (Yf, Yr); and an accelerating step for accelerating the drum rotational speed to a target rotational speed that is set to be higher than the reference rotational speed and the rotational speed causing resonance, when the front UB mass (mf) and the rear UB mass (mr) are in a preset allowable mass range and an angle between the two UB masses is in an allowable angle range, characterised in that the allowable mass range is set as a range of the front UB masses (mf) and a range of the rear UB mass (mr) in which the vibration generated in the tub is not out of a predetermined allowable vibration range, when the drum having a mass secured to the front and rear spaces of the drum is rotated at the target rotational speed, and wherein the allowable angle range is set as an angle between the front UB mass (mf) and the rear UB mass (mr) in which the vibration generated in the tub is not out of the allowable vibration range, when the drum having a UB mass within the allowable mass range is rotated at the target rotational speed. a maintaining step for rotating the drum at a reference rotational speed that is set to be a lower or a higher rotation than a rotational speed causing resonance in the laundry treating apparatus; a measuring step for controlling the sensing unit to measure the maximum displacement (Yf) of a tub front surface, the maximum displacement (Yr) of a tub rear surface and a phase difference (θ) between the maximum displacements (Yf, Yr) during the rotation of the drum at the reference rotational speed; a determining step (S50, S60) for determining a front UB mass (mf) located in a drum front area, a rear UB mass (mr) located in a drum rear area and an angle between the UB masses based on the maximum displacement (Yf) of the tub front surface, the maximum displacement (Yr) of the tub rear surface and the phase difference (θ) between the maximum displacements (Yf, Yr); and an accelerating step for accelerating the drum rotational speed to a target rotational speed that is set to be higher than the reference rotational speed and the rotational speed causing resonance, when the front UB mass (mf) and the rear UB mass (mr) are in a preset allowable mass range and an angle between the two UB masses is in an allowable angle range, characterised in that the allowable mass range is set as a range of the front UB masses (mf) and a range of the rear UB mass (mr) in which the vibration generated in the tub is not out of a predetermined allowable vibration range, when the drum having a mass secured to the front and rear spaces of the drum is rotated at the target rotational speed, and wherein the allowable angle range is set as an angle between the front UB mass (mf) and the rear UB mass (mr) in which the vibration generated in the tub is not out of the allowable vibration range, when the drum having a UB mass within the allowable mass range is rotated at the target rotational speed.