In this paper, a novel method for data hiding into binary images is proposed. Binary image has two tones: black and white. For this reason, it is not easy to hide messages into binary images. PWLC (pair-wise logical computation) is a new method to hide message into binary images. However, it yields images of unacceptable quality and its decoding process is unclear. Therefore, in order to solve this problem, we adopt the run-length method to achieve advanced reversible data hiding. That is, we find a proper region to hide messages to reduce visual degradation. In this paper, we introduce an improved procedure to hide messages into binary images.