To rapidly and easily check the trouble of a digital voice recorder even before recording of digital voices.

A specified current is applied to respective light sources 14 and the light quantities thereof are measured by an optical sensor 15 to obtain the measured light quantities at the time of first measuring the light quantities of the respective light sources 14 by a photosensor 15 when the specified current are applied thereto, storing the light quantities thereof as reference light quantities into the digital voice recording system and judging the deterioration of the respective light sources 14. The measured light quantities of the respective light sources 14 and the reference light quantities are compared by each piece. If the results thereof indicate that the light quantity decreases at a specified ratio, the light source 14 is decided to be deteriorated and the location of the deteriorated light source 14 is displayed. The deterioration or trouble of the respective light sources 14 is thus judged.