Provided are a steel sheet and a steel pipe having excellent HIC resistance that are ideal for, for instance, a line pipe used to convey petroleum or natural gas. The steel sheet and the steel pipe are formed from steel having a steel composition that comprises C: 0.02-0.08%, Si: 0.01-0.5%, Mn: 1.0-1.6%, Nb: 0.001-0.10%, Ca: 0.0001-0.0050%, N: 0.0010-0.0050%, and O: 0.0001-0.0030%, P: 0.01% or less, S: 0.0020% or less, Al: 0.030% or less, and Ti: 0.030% or less and that satisfies S/C a < 0.5, and having an unpressed portion of the part where center segregation occurs that is 0.1 mm or less in length.