Progress in flat panel displays (FPD) with requirements for larger size and thinner sheet glass has caused problems with regard to breakage or turnover operation, which require scribing to break the cell glass. To resolve these problems, a breakless scribing wheel was developed that has the ability to propagate deeper median cracks compared with conventional methods. Previously, median crack propagation with a scribing wheel, including the breakless wheel, has been observed only statically. Therefore, the median crack propagation with the breakless wheel was observed using a high-speed camera. The results indicated rapid median crack propagation up to 60% of the glass thickness within 0.02 s after passage of the wheel, and propagation speed decreased after 0.02 s.