A drum type washing machine and a method of detecting laundry weight thereof that is capable of calculating a ratio of input voltage applied to a motor through phase control until the motor reaches a determined number of rotations to accurately detect the weight of laundry or the amount of eccentricity of the laundry received in a drum connected to the motor. The drum type washing machine comprises a motor for rotating a drum, and a control unit for controlling the number of rotations of the motor depending upon a washing operation and calculating a ratio of input voltage applied to the motor, i.e., a modified voltage value, to determine the weight of laundry received in the drum. The weight of laundry received in the drum is accurately detected in steps, and therefore, water consumption is reduced, and a uniform washing operation is performed.