An integrated structure of MEMS device and CIS device and a fabricating method thereof includes providing a substrate having a CIS region and a MEMS region defined therein with a plurality of CIS devices positioned in the CIS region; performing a multilevel interconnect process to form a multilevel interconnect structure in the CIS region and the MEMS region and a micro-machined mesh metal in the MEMS region on a front side of the substrate; performing a first etching process to form a chamber in MEMS region in the front side of the substrate; forming a first mask pattern and a second mask pattern respectively in the CIS region and the MEMS region on a back side of the substrate; and performing a second etching process to form a plurality of vent holes connecting to the chamber on the back side of the substrate through the second mask pattern.