To provide a tube cap which is easy to attach to/detach from an end of a tube, which can reliably prevent earth and sand or the like from flowing in and which also has a drainage function.

The cap 10 has a disk 11 to be placed in an orthogonal direction to an axial direction of the tube 1, an annular wall 12 standing from a periphery of the disk 11, a flange 13 expanding outward from an end rim of the annular wall 12, a knob 14 protruding from the disk 11 and an opening 15 provided on a downward surface of the knob 14.