A sliding mechanism (6) includes a main board (10) and a sliding board (20). The main board has a body (11). A guiding rail (112) is formed at each of two opposite sides of the body. The sliding board has a first portion (21) and a second portion (22). The first portion has a first guiding slot (216) defined in a first end thereof for receiving one guiding rail. A bottom slice extends from a second opposite end of the first portion. The second portion has a second guiding slot (226) defined in a first end thereof for receiving the other guiding rail. A top slice extends from a second opposite end of the second portion. The top slice is located on the bottom slice. Before connecting the first portion and the second portion, a clearance between the guiding rail and the first portion can be adjusted.