A system that assists in treatment, the system comprising a control section (21, 31) configured to generate three-dimensional body data of a patient using data obtained from a three-dimensional measurement unit, which includes a depth sensor, wherein the three-dimensional body data is a three-dimensional model related to a body shape having information related to a body surface, obtain a tomographic image of the patient from a body tomographic measurement apparatus, wherein the system further comprises a treatment planning device, which is configured to extract contours using the tomographic image to produce a contour extraction result, characterised in that: the control section (21, 31) is further configured to generate body contour data in a format that is the same as the tomographic image based on the three-dimensional body data, execute an examination assist process, which aligns the three-dimensional body data with the tomographic image, i.e. the body contour data with the contour extraction result of the tomographic image, generate combination data in which the body contour data is combined with the tomographic image, execute a treatment plan assist process, which makes a treatment plan using the tomographic image and the three-dimensional body data that are aligned with each other, namely the combination data, wherein the treatment plan specifies a treatment performed by a treatment apparatus to an affected region of the tomographic image and a posture of the patient when treatment is performed, and execute a treatment assist process, which outputs a treatment instruction based on the posture of the patient specified in the treatment plan, wherein the control section (21, 31) is configured to execute a process for aligning the posture of the patient formed during an examination with the posture of the patient formed during the treatment and to provide the treatment plan for the treatment apparatus. the control section (21, 31) is further configured to generate body contour data in a format that is the same as the tomographic image based on the three-dimensional body data, execute an examination assist process, which aligns the three-dimensional body data with the tomographic image, i.e. the body contour data with the contour extraction result of the tomographic image, generate combination data in which the body contour data is combined with the tomographic image, execute a treatment plan assist process, which makes a treatment plan using the tomographic image and the three-dimensional body data that are aligned with each other, namely the combination data, wherein the treatment plan specifies a treatment performed by a treatment apparatus to an affected region of the tomographic image and a posture of the patient when treatment is performed, and execute a treatment assist process, which outputs a treatment instruction based on the posture of the patient specified in the treatment plan, wherein the control section (21, 31) is configured to execute a process for aligning the posture of the patient formed during an examination with the posture of the patient formed during the treatment and to provide the treatment plan for the treatment apparatus.