The present invention relates to a thin film transistor array panel and a manufacturing method thereof that prevent disconnection of wiring due to misalignment of a mask, and simplify a process and reduce cost by reducing the number of masks. The thin film transistor array panel according to the disclosure includes a source electrode enclosing an outer part of the first contact hole and formed on the second insulating layer; a drain electrode enclosing an outer part of the second contact hole and formed on the second insulating layer; a first connection electrode connecting the source region of the semiconductor layer and the source electrode through the first contact hole; and a second connection electrode connecting the drain region of the semiconductor layer and the drain electrode through the second contact hole.