Treatment planning system, device for calculating a scanning path and particle therapy system

A treatment planning system for creating treatment plan information for particle therapy, comprising:

• an input device;
• an arithmetic device for performing arithmetic processing based on a result of input to the input device and creating treatment plan information;
• and
• a display device for displaying the treatment plan information,
• wherein the arithmetic device calculates a scanning path by setting a pre-specified direction as a main direction for scanning irradiation positions with an ion beam using scanning magnets, the pre-specified direction being along a direction of movement of a target of treatment, and
• wherein the display device displays the direction of movement of the target of treatment.