A resin composition includes a cellulose ester resin having a weight average molecular weight of 10,000 to 75,000; sulfuric acid; and at least one metal element selected from the group consisting of Group 1 elements and Group 2 elements, wherein a ratio of the sum of the content [M1] of the Group 1 element and the content [M2] of the Group 2 element to the total amount of all the elements according to fluorescent X-ray spectroscopy is 0.052% by weight, and a molar ratio of the content [M1] of the Group 1 element, the content [M2] of the Group 2 element, and the content [S] of sulfur atoms (S) according to fluorescent X-ray spectroscopy satisfies a relationship of Expression 1: ([M1]/2)+[M2]≥1.5×[S].