The present invention relates to an impedance transformation-type wide band internal antenna. The wide band antenna includes a radiation part, a short circuit part, a feeding part, and a feeding pin. The radiation part is formed to have a predetermined length and width according to an operating frequency, the radiation part including a plurality of stubs formed in arbitrary shapes according to location of a plurality of slots. The short circuit part causes part of a side surface of the radiation part to be connected to an external ground. The feeding part is extended from the stubs, formed on the side surface of the radiation part to be adjacent to the short circuit part, and is bent multiple times, the feeding part being formed on a bottom surface of the radiation part to have a predetermined length and width. The feeding pin is formed on an end of the feeding part and is fed with current. Accordingly, the present invention is advantageous in that impedances are matched using the length and interval of the feeding part, which is bent multiple times, and the size of a through hole formed in the feeding part, so that a plurality of wide band resonant frequencies is formed, thus enabling the wide band antenna to be simultaneously used for different frequency bands in a wireless communication system that uses different frequency bands.