To provide a key cylinder device equipped with a handle lock mechanism which can maintain a handle lock mechanism of a key cylinder unit with a shutter to provide an improved assembleability of the key cylinder device. The bolts for fixing a shutter housing are attached from the back surface of the top plate of an inverted angular U-shaped bracket. Thus, even when a gap is generated between the shutter housing and a vehicle body cover, the bolts are not exposed and hence cannot be easily loosened. In addition, by mounting the key cylinder device in the vehicle body cover and then mounting the vehicle body cover thereon, assembleability can be improved.