A sliding protective device for an electronic product having a first portion and a second portion is disclosed. The protective device comprises a top cover, a bottom cover, a fixing element, and a sliding element, wherein the fixing element is provided at an inner surface of one of the aforementioned covers to be fixed to the first portion of the electronic product; the sliding element is provided at an inner surface of the other one of the aforementioned covers to be slidably engaged with two lateral sides of the second portion of the electronic product; whereby, when the electronic product is being opened, the second portion of the electronic product can slide along the sliding element, so that the protective device can be always smoothly attached to the outer surfaces of the electronic product, so that the protective device can be prevented from being bulged or wrinkled.