An SMC manufacturing method comprising: (i) drawing out a continuous carbon fiber bundle from a package, the continuous carbon fiber bundle having a filament number of NK and partially split into n sub-bundles in advance; (ii) forming chopped carbon fiber bundles by chopping the continuous carbon fiber bundle drawn out from the package with a rotary cutter; (iii) forming a carbon fiber mat by depositing the chopped carbon fiber bundles on a carrier film traveling below the rotary cutter; and (iv) impregnating the carbon fiber mat with a thermosetting resin composition, wherein fragmentation processing using a fragmentation processing apparatus below is performed on the chopped carbon fiber bundles before being deposited on the carrier film, the fragmentation processing apparatus comprising a first pin roller and a second pin roller, each of which has a rotation axis parallel to a rotation axis direction of the rotary cutter, a sum of a maximum radius of the first pin roller and a maximum radius of the second pin roller is larger than the distance between the rotation axes of the first pin roller and the second pin roller, and the first pin roller is rotationally driven such that its pins move downward from above on its side facing the second pin roller, and the second pin roller is rotationally driven such that its pins move downward from above on its side facing the first pin roller. (i) drawing out a continuous carbon fiber bundle from a package, the continuous carbon fiber bundle having a filament number of NK and partially split into n sub-bundles in advance; (ii) forming chopped carbon fiber bundles by chopping the continuous carbon fiber bundle drawn out from the package with a rotary cutter; (iii) forming a carbon fiber mat by depositing the chopped carbon fiber bundles on a carrier film traveling below the rotary cutter; and (iv) impregnating the carbon fiber mat with a thermosetting resin composition, wherein fragmentation processing using a fragmentation processing apparatus below is performed on the chopped carbon fiber bundles before being deposited on the carrier film, the fragmentation processing apparatus comprising a first pin roller and a second pin roller, each of which has a rotation axis parallel to a rotation axis direction of the rotary cutter, a sum of a maximum radius of the first pin roller and a maximum radius of the second pin roller is larger than the distance between the rotation axes of the first pin roller and the second pin roller, and the first pin roller is rotationally driven such that its pins move downward from above on its side facing the second pin roller, and the second pin roller is rotationally driven such that its pins move downward from above on its side facing the first pin roller. wherein fragmentation processing using a fragmentation processing apparatus below is performed on the chopped carbon fiber bundles before being deposited on the carrier film, the fragmentation processing apparatus comprising a first pin roller and a second pin roller, each of which has a rotation axis parallel to a rotation axis direction of the rotary cutter, a sum of a maximum radius of the first pin roller and a maximum radius of the second pin roller is larger than the distance between the rotation axes of the first pin roller and the second pin roller, and the first pin roller is rotationally driven such that its pins move downward from above on its side facing the second pin roller, and the second pin roller is rotationally driven such that its pins move downward from above on its side facing the first pin roller.