To provide a side exterior panel device for a passenger conveyor that can mount a side exterior panel on the outside of a main frame via a simple operation at an installation field.

A pressing portion 24 of an elastic mounting element 19 fitted on an outer deck 9 deforms elastically to press an upper edge of the side exterior panel 16 against a stopping portion 10 of the outer deck 9 and to mount the side exterior panel 16 on the outer deck 9. The structure, wherein the elastic mounting element 19 is easily mountable and serves as a guide, and a manufacturing error in the thickness of the side exterior panel 16 including the thicknesses of an upper reinforcement 11 and a vertical reinforcement 18 is absorbable, can facilitate the mounting of the side exterior panel 16 on the outer deck 9. The mounting operation of the side exterior panel 16 is facilitated and the cost thereof is reduced.