The present invention relates to a maraging steel containing, in terms of mass %, 0.10≤C≤0.35, 9.0≤Co≤20.0, 1.0≤(Mo+W/2)≤2.0, 1.0≤Cr≤4.0, a certain amount of Ni, a certain amount of Al, and V+Nb≤0.60, with the balance being Fe and inevitable impurities, in which in a case of V+Nb≤0.020, the amount of Ni is 6.0≤Ni≤9.4 and the amount of Al is 1.4≤Al≤2.0, and in a case of 0.020