To always display the latest information by eliminating the need of a trouble shooting manual and to perform support by telephone even to a customer who cannot solve the problem using displayed trouble shooting information only.

This failure diagnostic system of a motor controller is provided with an inverter provided with an operator 5 that can display information, a terminal 7 provided with a two-dimensional code reading means and an accessing means to an Internet homepage, and a homepage server 9 provided with a trouble shooting database 10. The two-dimensional code includes Internet homepage address information of the homepage server, and when the two-dimensional code reading means reads the two-dimensional code, the access means accesses the Internet homepage and displays information of the trouble shooting database on an information display means of the terminal.