A loop antenna adapted for a communication device is provided. The loop antenna includes a feed, a ground, a circular loop, at least one first tuning element, and at least one second tuning element. The circular loop is connected to the feed and the ground. The first tuning element is extended from the circular loop and corresponds to a first frequency band. The second tuning element is extended from the circular loop and corresponds to a second frequency band. Bandwidths of the first frequency band and the second frequency band of the loop antenna are changed by adjusting the first tuning element and the second tuning element, respectively.