To close a guide groove when a shutter is opened, and promote traffic safety by arranging laterally sliding shielding plates and an opening-closing mechanism energized by springs in a frame body of a floor surface guide rail.

Laterally sliding shielding plates 6 and 6' are arranged in clearances 7 and 7' between an upper plate 2 of a floor surface guide rail frame body 1 and the upper edge of a U-shaped plate 4 of a guide groove 3. One swinging pieces and the other swinging pieces of the upper hinges 9 and 9' installed on under surfaces of the shielding plates 6 and 6' and of the lower hinges 11 and 11' which are fixed to installing pieces 5a and 5b of a bottom plate and energized by springs 13 and 13', are connected to each other by connecting pieces 14 and 14', and are housed in the mechanism housing parts 8 and 8' of the shielding plates. When a shutter S travels, a support opens the guide groove 3 by pressing and sliding the shielding plates 6 and 6' against the springs 13 and 13'. The shutter S is opened, and when the guide groove 3 is opened, the springs 13 and 13' push back the shielding plates 6 and 6', and are joined and closed in a central part of the guide groove 3, and hold traffic safety.