A pressure gauge includes a base including an annular flange and a pipe for gas flow; a ring on the flange; an uneven pressure measuring member on the ring; a moveable assembly including a seat, a hollow insert, and a shaft wherein the seat is secured to the pressure measuring member, the insert includes two opposite, internal, upper projections, the insert is fastened in the seat, the shaft includes external threads secured to the projections, an upper annular groove, a top protrusion, and an axis projects upward from the protrusion; a pointer secured to the axis; a covering member includes a ring member on the pressure measuring member, and a bridge crossing the ring member and allowing the axis to pass through, and a bent member; a balance spring in the groove and fastened in the bent member; a scale on the bridge; a housing; and a transparent cover.