Burst tests of line pipes containing high-pressure hydrogen and methane gas were conducted. The pipes tested were X65 ERW pipes with 267mm outer diameter and 6mm wall thickness. Applied pressures were 12MPa. A 300mm long crack was initiated by a shaped charge. Unstable shear fracture propagated at velocity of approximately 200m/s and then arrested. It was demonstrated that the arrested crack lengths were shorter in the hydrogen gas burst tests than methane gas burst tests. Pressure measurement indicated that the decompression wave in hydrogen gas propagated about four times faster than that in methane gas. This is probably the primary reason to the shorter arrested crack lengths for the hydrogen gas tests.