To provide a steel and a manufacturing method thereof that can contribute to achieving both high strength and hydrogen embrittlement resistance. The steel has a chemical composition represented by: C: 0.15% to 0.35%; Si: 0.8% to 2.5%; Mn: 0.8% to 2.5%; Al: 0.03% to 2.0%; N: 0.002% to 0.010%; P: 0.01% or less; S: 0.01% or less; O: 0.01% or less; B: 0.0001% to 0.005%; Nb: 0.0% to 0.05%; Ti: 0.0% to 0.2%; V 0.0% to 0.05%; Mo: 0.0% to 1.0%; Cr: 0.0% to 1.0%; Ni: 0.01% to 1.0%; Cu: 0.05% to 1.0%; at least one of Ca, Mg and REM: 0.0005% to 0.01%; and the balance: Fe and impurities, and has a martensite phase or/and a bainite phase in which ε-carbide is dispersedly precipitated.