A spout unit having a tamper-evident function so that it is easy to determine visually that a sealed cap is opened when the cap is unsealed, wherein strong force is not needed to open while modification of moderate curve in convex from an easy-to-break portion of a tamper-proof ring is corrected when the spout is sealed with the cap, is provided. A spout unit comprising a spout 20 having a cylindrical opening 21 and a cap 2 which seals the opening of the spout, wherein the cap 2 has a tamper-proof ring 10 connected to a lower end portion of the cap 2 via an easy-to-break linking piece; wherein the tamper-proof ring has an easy-to-break portion 14, which breaks by tension applied in the circumferential direction of the ring, and a claw part engageable with a ratchet provided at the spout side; and wherein a tamper-proof ring support 45 is provided at least at two points around the opening of the spout, in which the tamper-proof ring support is in partial contact with undersurface of the tamper-proof ring upon screwing the cap and has a height to maintain a position of the tamper-proof ring in horizontal direction at a constant level.