An ultrasound treatment device, comprising: a diagnosis ultrasound transmitter for transmitting ultrasound with intensity for diagnosis; a treatment ultrasound transmitter for transmitting ultrasound with intensity for treatment which is stronger than the intensity for diagnosis from a transmission position which is substantially the same as a transmission position of the diagnosis ultrasound transmitter; a sequence controller that causes the treatment ultrasound transmitter to transmit the ultrasound with intensity for treatment during a treatment period and also causes the diagnosis ultrasound transmitter to transmit the ultrasound with intensity for diagnosis at each inspection timing that satisfies a predetermined condition, thereby generating a diagnosis image at the inspection timing; a vital signal detector that provides a periodic vital signal output corresponding to a periodical movement of an organ to be treated, wherein the vital signal detector comprises an electrocardiograph or a respiration monitor; a shift detection unit that detects a positional shift of a treatment target portion, based on comparison between a diagnostic image generated at a certain inspection timing and a diagnostic image which has been generated at an inspection timing prior to the certain inspection timing and stored, wherein the diagnostic images (130A, 130B) are captured when the organ is in the same motion state in its periodic movement pattern based on the periodic vital signal output; and a shift correction processing unit that performs predetermined shift correction processing when a positional shift of the treatment target portion is detected by the shift detection unit, wherein the sequence controller selects, as the inspection timing that satisfies a predetermined condition, a timing point at which a time phase of a movement of the organ which is obtained from the periodic vital signal detected by the vital signal detector corresponds to a predetermined time phase, the timing point being near a time point after which it is detected that a predetermined unit treatment time has elapsed from the previous inspection timing. a diagnosis ultrasound transmitter for transmitting ultrasound with intensity for diagnosis; a treatment ultrasound transmitter for transmitting ultrasound with intensity for treatment which is stronger than the intensity for diagnosis from a transmission position which is substantially the same as a transmission position of the diagnosis ultrasound transmitter; a sequence controller that causes the treatment ultrasound transmitter to transmit the ultrasound with intensity for treatment during a treatment period and also causes the diagnosis ultrasound transmitter to transmit the ultrasound with intensity for diagnosis at each inspection timing that satisfies a predetermined condition, thereby generating a diagnosis image at the inspection timing; a vital signal detector that provides a periodic vital signal output corresponding to a periodical movement of an organ to be treated, wherein the vital signal detector comprises an electrocardiograph or a respiration monitor; a shift detection unit that detects a positional shift of a treatment target portion, based on comparison between a diagnostic image generated at a certain inspection timing and a diagnostic image which has been generated at an inspection timing prior to the certain inspection timing and stored, wherein the diagnostic images (130A, 130B) are captured when the organ is in the same motion state in its periodic movement pattern based on the periodic vital signal output; and a shift correction processing unit that performs predetermined shift correction processing when a positional shift of the treatment target portion is detected by the shift detection unit, wherein the sequence controller selects, as the inspection timing that satisfies a predetermined condition, a timing point at which a time phase of a movement of the organ which is obtained from the periodic vital signal detected by the vital signal detector corresponds to a predetermined time phase, the timing point being near a time point after which it is detected that a predetermined unit treatment time has elapsed from the previous inspection timing.