A pressure indicator with a pressure-relief function is disclosed, which can release excessive pressure to the environment. The pressure indicator includes a transparent tube defining therein a first bore and a second bore, and a slider which can be forced by the medium supplied from an external pressure source to move along the first and second bores of the transparent tube. In particular, the first bore has a diameter greater than the second bore, and a tapered annular surface is provided between the first bore and the second bore of the transparent tube. When the pressure of the medium exceeds a predetermined pressure, the slider can be forced by the medium to reach the tapered annular surface, at which excessive medium can be released into the environment via an annular gap between the slider and the tapered annular surface.