The utility model relates to the technical field of flatness detection, and discloses a tunnel side wall flatness detection device, which comprises a
parallel plate, the outer surface of the
parallel plate is provided with a detection mechanism, the back surface of the
parallel plate is fixedly connected with a lug block, the interior of the lug block is slidably connected with an extension rod, one end of the extension rod is fixedly connected with a side wall sliding mechanism, and the other end of the extension rod is fixedly connected with a side wall sliding mechanism. A plurality of screw holes are formed in the outer surface of the extension rod, and the outer surfaces of the lug blocks are in threaded connection with locking rotary knobs. An operator holds the
handle to push the device to move, so that the
steel ball is attached to the side wall, if the side wall is flat, the displacement amount detected by the displacement sensor is normal, and the alarm lamp is not turned on, and if the side wall is concave-convex, the
steel ball drives the measuring rod to stretch out and draw back, and the displacement sensor detects abnormal displacement change, and the alarm lamp is turned on. The flatness of the side wall of the tunnel is rapidly judged in a visual alarm mode, and the detection work efficiency and convenience are improved.