A fiber-reinforced thermoplastic-resin base includes continuous reinforcing fibers aligned in parallel to each other and a thermoplastic resin is impregnated thereinto, wherein the base has a fiber volume content of 40-65 vol % and a dispersion parameter D of the fibers, determined by (i)-(iv), of 90% or more: (i) a cross-section of the fiber-reinforced thermoplastic-resin base that is perpendicular to the alignment direction of the reinforcing fibers is divided into a plurality of sections, and one of the sections is photographed, (ii) the photograph image of the section is divided into a plurality of square units each having a one-side length t, (iii) a dispersion parameter d is calculated, (iv) with respect to other sections, (i) to (iii) are repeatedly performed, and an average value of dispersion parameters d of the plurality of sections is dispersion parameter D.