A whiteboard comprises a panel, four rims and four connectors. The panel comprises a writable pre-coating layer, a foaming layer and a back plate. The each rim comprises a rim main body and a number of locking pieces. The rim main body comprises a top plate, a light filter plate, an upper plate, a side plate. The light filter plate is connected between the top plate and the upper plate by melting. An inserting plate is vertically extended outwards from the side plate. A locking plate is vertically extended downwards from the rear end of the inserting plate. The locking pieces are locked at the lower ends of the locking plates. Each of the locking pieces comprises a connecting portion at the upper position thereof. A supporting portion is formed at the lower end of the connecting portion. The each connector comprises a bottom casing and a top casing. The bottom casing comprises a bottom casing main body. The top casing comprises a top cover. A lateral plate is downwards bent and extended from the outer edge of the top cover. A sealing strip is pasted at the position of the inner edge of the sealing strip contacting the writable pre-coating layer.