To provide a normality testing method and a normality testing device capable of easily confirming a phase error and the stepping state of a built-in clock of a new time signal guide device to Japan Standard Time.

When a maintenance terminal is not connected to the new time signal guide device 1, the phase error of a one sec TAE pulse synchronized with the time of the built-in clock outputted from a first output terminal 12a of a serial connector 12 and a one sec GPS pulse received by a GPS receiver 8 via a GPS antenna 6 is measured by a phase comparing circuit 9 of a phase error tester 7 to be displayed on a display part 10, and when the maintenance terminal is not connected to the new time signal guide device 1 serial time information on the built-in clock outputted from a second output terminal 12b of the serial connector 12 is introduced to a personal computer 15 of a time confirming communication terminal 4, and the serial time information and information on the Japanese Standard Time are displayed in parallel on a display device to confirm the stepping state of the built-in clock.