An antenna is provided and includes a first antenna structure, a signal reflection structure, and an assembling unit. The first antenna structure has a first positioning portion and a radiator having a free end. The signal reflection structure has a second positioning portion, in which the signal reflection structure is configured to be assembled with the first antenna structure, and the first positioning portion corresponds with the second positioning portion. The assembling unit is for assembling the first antenna structure and the signal reflection structure in conjunction with the first and second positioning portions. The inner edge is configured to abut against the first antenna structure and the signal reflection structure. The receiving groove is located at one of the end portions of the assembling unit, in which the receiving groove is capable of receiving the free end of the radiator in order to limit its movement.