A separation composite membrane including: a separating layer for separating fluid components, the separating layer being constituted of a polymer having cross-linked structure, and a porous layer for supporting the separating layer, the porous layer having a maximum pore diameter of 0.05 to 0.5 μm, the separating layer being partly impregnated into the porous layer in the range of 0.1 to 30% in terms of the impregnation amount ratio (ηa) defined by Formula (A): [impregnation amount ratio (ηa) {% }=impregnation depth (s)/(membrane thickness (t1) of separating layer)×100]  (A).