An opening/closing device (10, 100) for electronic devices comprising: an opening/closing mechanism (11A, 11B, 111A, 111B) wherein a movable plate (14, 114A, 114B) is moved between an opened position and a closed position with respect to a fixed plate (12, 16, 112, 116), the opening/closing mechanism (11A, 11B, 111A, 111B)including a hinge arm including a first axial portion rotatably connected to the fixed plate (12, 16, 112, 116), a third axial portion rotatably connected to the movable plate (14, 114A, 114B), and a slide groove provided between the first axial portion and the third axial portion, and capable of moving the movable plate (14, 114A, 114B) between the closed position and the opened position with respect to the fixed plate (12, 16, 112, 116) by being rotated around the first axial portion as a center, a link arm including a second axial portion rotatably connected to the fixed plate (12, 16, 112, 116) and a fifth axial portion slidably connected to the slide groove, and a slide arm including a fourth axial portion rotatably connected to the movable plate (14, 114A, 114B) at an end portion and connected to the fifth axial portion at the other end portion, and wherein when the movable plate (14, 114A, 114B) is moved between the closed position and the opened position, the fifth axial portion is slid in the slide groove in accordance with rotations of the hinge arm and the link arm, and surfaces of the first housing and the second housing are positioned at substantially the same plane when the movable plate (14, 114A, 114B) is moved to the opened position. an opening/closing mechanism (11A, 11B, 111A, 111B) wherein a movable plate (14, 114A, 114B) is moved between an opened position and a closed position with respect to a fixed plate (12, 16, 112, 116), the opening/closing mechanism (11A, 11B, 111A, 111B)including a hinge arm including a first axial portion rotatably connected to the fixed plate (12, 16, 112, 116), a third axial portion rotatably connected to the movable plate (14, 114A, 114B), and a slide groove provided between the first axial portion and the third axial portion, and capable of moving the movable plate (14, 114A, 114B) between the closed position and the opened position with respect to the fixed plate (12, 16, 112, 116) by being rotated around the first axial portion as a center, a link arm including a second axial portion rotatably connected to the fixed plate (12, 16, 112, 116) and a fifth axial portion slidably connected to the slide groove, and a slide arm including a fourth axial portion rotatably connected to the movable plate (14, 114A, 114B) at an end portion and connected to the fifth axial portion at the other end portion, and a hinge arm including a first axial portion rotatably connected to the fixed plate (12, 16, 112, 116), a third axial portion rotatably connected to the movable plate (14, 114A, 114B), and a slide groove provided between the first axial portion and the third axial portion, and capable of moving the movable plate (14, 114A, 114B) between the closed position and the opened position with respect to the fixed plate (12, 16, 112, 116) by being rotated around the first axial portion as a center, a link arm including a second axial portion rotatably connected to the fixed plate (12, 16, 112, 116) and a fifth axial portion slidably connected to the slide groove, and a slide arm including a fourth axial portion rotatably connected to the movable plate (14, 114A, 114B) at an end portion and connected to the fifth axial portion at the other end portion, and wherein when the movable plate (14, 114A, 114B) is moved between the closed position and the opened position, the fifth axial portion is slid in the slide groove in accordance with rotations of the hinge arm and the link arm, and surfaces of the first housing and the second housing are positioned at substantially the same plane when the movable plate (14, 114A, 114B) is moved to the opened position.