To provide a top-railed sliding door device shortening the depth of a part under a floor face for housing a guide pin, preventing accumulation of dust at the guide pin, which hardly hinders its operation, and having excellent maintenance performance and designability on the floor face.

The top-railed sliding door device includes the guide pin 5 provided on the floor face 4 in a protruding and retreating manner. The guide pin 5 is protruded by a magnetic force and inserted into a traveling groove 6, being formed on the lower edge of a top-railed sliding door 1, so that traveling guide may be performed. A guide device main body 7 opening upward is buried under the floor face 4. The guide pin 5 is housed in the guide device main body 7 to be protrudable upward. The guide pin 5 comprises a first guide member 9 having a magnet 8 at its upper end, and a second guide member 10 opening upward so that the first guide member 9 may be fittedly housed therein to be protrudable upward in a telescopic manner in a vertical direction. An extended diametral top member 11 having a larger diameter than that of the upper opening of the second guide member 10 is formed on the upper end of the first guide member 9.