The present invention relates to a security device for detecting an intrusion including at least one sensor frame including a sensor, a first connection frame for connecting a signal sensed from the sensor frame, and a signal processing frame for detecting an intrusion from the sensed signal received from the first connection frame or the sensor frame, wherein the at least one sensor frame is detachably connected to the security device. Accordingly, the security device can be easily installed, use a variety of sensors, and be changed in size.