A ventilated type brake disc rotor includes: a pair of sliding plates shaped annular and disposed opposite to each other in an axle direction; and joints formed to connect between the sliding plates and arranged along lines extending in a circumferential direction of the sliding plates. The joints include first joints arranged along a first line and second joints arranged along a second line located in an outer side with respect to the first line in a radial direction of the sliding plates. Each of the second joints includes a first width part and a second width part formed in an inner side with respect to the first width part in the radial direction. The second width part is less in circumferential width than the first width part, and is shaped to decrease in circumferential width as going inwardly in the radial direction.