A manufacturing method of a thin film transistor and a thin film transistor are provided. In the manufacturing method, formation of pattern of a source electrode (7), a drain electrode (8) and an active layer (6) comprises: forming a semiconductor layer (10) and a conductive layer (11) that cover the whole substrate on the substrate in sequence; forming a first photoresist layer (4) at a region where the source electrode is to be formed and at a region where the drain electrode is to be formed on the conductive layer (11), respectively; forming a second photoresist layer (5) at least at a gap between the source electrode and the drain electrode that are to be formed on the conductive layer (11); conducting an etching process on the substrate with the first photoresist layer (4), the second photoresist layer (5), the semiconductor layer (10) and the conductive layer (11) formed thereon, so as to form pattern of the active layer (6), the source electrode (7) and the drain electrode (8).