A burglar alarm device has a body and a mounting bracket. The body has a casing, a rear cover and a detection and alarm assembly. The detection and alarm assembly is mounted on the rear cover inside the casing and has a vibration sensor and an illumination source. The body is attached to the optional mounting bracket. When a doorframe with the burglar alarm device is touched, the detection and alarm assembly will sound an audible alarm to warn people in the house, and the illumination source will light up. Further, the illumination source can be turned on to illuminate the keyhole so a person can easily insert a key.