The invention discloses a child safety lock device universal for a sash window and a casement window. The child safety lock device comprises a steel wire rope with the two ends fixedly connected with heavy blocks and a fixed pulley fixed to the upper wall of the interior of a sash frame; the child safety lock device further comprises an iron clamp with one end fixed to the side wall of the interior of a sash, the other non-fixed end of the iron clamp is connected with a first rotary button through a rope, the first rotary button is arranged on the side surface of the interior of the upper portion of a right sash body of the sash window or the casement window, and the heavy blocks at the two ends of the steel wire rope are the same in material and weight; the child safety lock device also comprises a gear and rack mechanism, the upper end of a rack abuts against the heavy block at the right sash body, a gear shaft of a gear meshed with the rack is fixedly connected with a second rotary button, and the second rotary button is arranged on the side surface of the interior of the upper portion of the right sash body of the sash window or the casement window; and the height of the heavy block at the position of a left sash body is larger than the height of the heavy block at the position of the right sash. According to the child safety lock device, the two sashes are connected through the steel wire rope, the window can be opened by a certain distance through the arrangement of a limiting device, and the child safety lock device can be used for both the sash window and the casement window.