An opening and closing mechanism for a keyboard cover that includes a front cover half and a rear cover half coupled foldably by a hinge. The mechanism comprises a first guide that guides the front cover half backward at a front end thereof along the keyboard when the cover is opened and a second guide that backward guides the rear cover half at a front edge thereof along the keyboard and guides the rear cover half obliquely downward at a rear end thereof after the keyboard, thereby rendering the rear cover half upstanding when the cover is opened. Thus, the second guide prevents the rear and front cover halves from lowering at their front and rear ends, respectively, thereby allowing the keyboard cover to be opened and closed smoothly.