To provide a sliding mechanism capable of thinning a portable device.

The sliding mechanism includes a projecting part 11 provided on either one of a first casing 1 and a second casing 2; a recess part 12 for slidably housing a projecting part 11 provided on the other of the casings; a rail 13 for slidably engaging the recess part 12 and the projecting part 11; and a telescopic biasing means 15 for biasing the first casing 1 and the second casing 2 away from each other. Thus, the projecting part 11 slides within the recess part 12 while engaging the rail 13. More specifically, the projecting parts 11 are integrally formed on the right and left sides of one of the casings 1 and the recess parts 12 are formed on the right and left sides of the other casing 2. The rail 13 comprises a first rail 131 passing through the projecting part 11 and secured to the recess part 12, and a second rail 132 secured to the recess part 12 while being engaged in a groove formed in a side face of the projecting part 11.