The present invention provides an automatic speed control apparatus for a treadmill and the control method including a deck, a track belt of endlessly rotating on the upper and the bottom face of the deck, and a driving unit for driving unit for driving the track belt comprising: at least one front load sensor located in the front part of the track belt for measuring load from a user on the track belt; at least one rear load sensor located in the rear part of the track belt for measuring load from the user on the track belt, wherein the proceeding speed of the track belt is controlled based on the user's location or movement on the track belt by comparing the measured values from the front load sensor and the rear load sensor and catching the user's location based on the comparison therebetween, whereby the proceeding speed can be automatically controlled corresponding with the user's running speed without the user's direct operation.