To easily change the setting of a display environment in a gothic arch tracer system.

A processing part 10 of a gothic arch tracer system includes a CPU part 12 executing a process for describing a gothic arch; a display part 14 displaying the gothic arch; an input part 16 inputting orders regarding the display of the gothic arch; a main program 24 causing the CPU part 12 to execute the process for describing the gothic arch; and an environment setting program 25 setting a display environment for displaying the gothic arch on the display part 14 according to the orders regarding the display which are inputted from the input part 16. The main program 24 causes the CPU part 12 to execute the process for describing the gothic arch in accordance with the display environment set by the environment setting program 25, and causes the gothic arch to be displayed on the display part 14.