Method for manufacturing alloy steel powder for sintered member raw material

Provided is a method by which alloy steel powder containing easily oxidizable Cr or Mo as an alloying element is efficiently and stably manufactured via water atomizing. A method for manufacturing alloy steel powder for a sintered member material having a water atomizing step of water atomizing molten steel to obtain a water-atomized iron-base powder, and a heat treatment step for subjecting the water-atomized iron-base powder to a reducing heat treatment and obtaining an alloy steel powder; the alloy steel powder containing 0.3‒3.5% of Cr and more than 0.08% and no more than 1.0% of Mn (percentage amounts expressing mass) as the alloying element, and otherwise comprising Fe and inevitable impurities, the amount of C [C] (mass%) in the molten steel and the amounts of Cr [Cr], Mn [Mn], and V [V] (mass%) in the molten steel satisfying the relationship shown in formula (1). 0.07≦[C]/{[Cr] 2/3 +2([Mn]+[V])≦0.23 ... (1)