A base plate defines a portion of a housing of a disk drive device. The housing accommodates therein a disk, a spindle motor that rotationally drives the disk about a center axis that extends in a vertical direction, and an access portion that carries out at least one of reading or writing of information with respect to the disk. The base plate includes a cast metal base body and an electrodeposition coating film that covers the surface of the base body. The base body includes a bottom plate portion extending from the center axis to an outward in a radial direction and a wall portion with a rectangular or substantially rectangular shape viewed in the axial direction upward from an outer circumference portion of the bottom plate portion. An outside surface of the wall portion includes a coated surface covered with the electrodeposition coating film, a processing surface which is flat and on which a casting material is exposed from the electrodeposition coating film, and a parting line. The processing surface extends in the axial direction in contact with the parting line or across the parting line.