The present invention provides a magnetic doorstop, which is attached to the multidirectional joint of the existing sectional shelf. The doorstep includes a block type main part, which is of block type and has an mounting end and a holder; a clamp mouth, which is concave on the mounting end of the main part and displays a v-shape; and a magnetic part set on the holder of the main part. The magnetic doorstop can clamp the edge of corner recess of a multidirectional joint by the clamp mouth, and when the flexible door piece pivots to close, the magnetic part on the holder of the holding magnetic doorstop attracts the magnet at one corner of the frame bar of the flexible door piece and holds it. Thus, the flexible door piece can be held close.