A flexible negative pressure cup includes a body case having a boxlike shape, a flexible cup body, an air extracting pump, an inlet valve and a control box. The lower portion of the body case is connected with the upper portion of the flexible cup body for forming an air chamber between the bottom wall of the body case and the flexible cup body. The middle portion of the bottom of the flexible cup body is upwardly protruded. Two downwardly protruded annular buds are respectively formed at two end portions of the bottom of the flexible cup body. An air hole is provided on the bottom wall of the body case. The air hole is communicated with the air extracting pump and the inlet valve located outside the body case by a flexible tube. The control box is connected with the air extracting pump and the inlet valve.
