An air floating belt conveyor apparatus comprising: a conveyor main body (Cm) including an endless conveyor belt and configured to convey conveyed materials, placed on a conveyance surface of the conveyor belt, in a predetermined direction; a carrier route belt supporting body supporting a carrier route portion of the conveyor belt from below and including a plurality of air outlets through which air for making the conveyor belt float flows out to between an upper surface of the carrier route belt supporting body and a non-conveyance surface of the conveyor belt; at least one air supply header including a header chamber communicating with the plurality of air outlets, the at least one air supply header being provided at a lower portion of the carrier route belt supporting body; and a blower configured to supply the air to the air supply header, wherein the air supply header includes: an air supply port through which the air supplied from the blower is introduced to the header chamber; a discharge port provided at one or each of both longitudinal direction end portions of the air supply header, and an opening/closing device configured to open and close the discharge port, wherein the air floating belt conveyor apparatus further comprises: a return route belt supporting body located under the discharge port and supporting a return route portion of the conveyor belt; a belt inversion mechanism configured to invert the conveyor belt such that the conveyance surface of the conveyor belt passing through the return route belt supporting body faces upward; and wherein the dust accumulated in the header chamber being discharged through the discharge port together with the air falls on the conveyance surface of the return route portion of the conveyor belt. a conveyor main body (Cm) including an endless conveyor belt and configured to convey conveyed materials, placed on a conveyance surface of the conveyor belt, in a predetermined direction; a carrier route belt supporting body supporting a carrier route portion of the conveyor belt from below and including a plurality of air outlets through which air for making the conveyor belt float flows out to between an upper surface of the carrier route belt supporting body and a non-conveyance surface of the conveyor belt; at least one air supply header including a header chamber communicating with the plurality of air outlets, the at least one air supply header being provided at a lower portion of the carrier route belt supporting body; and a blower configured to supply the air to the air supply header, wherein the air supply header includes: an air supply port through which the air supplied from the blower is introduced to the header chamber; a discharge port provided at one or each of both longitudinal direction end portions of the air supply header, and an opening/closing device configured to open and close the discharge port, wherein the air floating belt conveyor apparatus further comprises: a return route belt supporting body located under the discharge port and supporting a return route portion of the conveyor belt; a belt inversion mechanism configured to invert the conveyor belt such that the conveyance surface of the conveyor belt passing through the return route belt supporting body faces upward; and wherein the dust accumulated in the header chamber being discharged through the discharge port together with the air falls on the conveyance surface of the return route portion of the conveyor belt. an air supply port through which the air supplied from the blower is introduced to the header chamber; a discharge port provided at one or each of both longitudinal direction end portions of the air supply header, and an opening/closing device configured to open and close the discharge port, wherein the air floating belt conveyor apparatus further comprises: a return route belt supporting body located under the discharge port and supporting a return route portion of the conveyor belt; a belt inversion mechanism configured to invert the conveyor belt such that the conveyance surface of the conveyor belt passing through the return route belt supporting body faces upward; and wherein the dust accumulated in the header chamber being discharged through the discharge port together with the air falls on the conveyance surface of the return route portion of the conveyor belt. a return route belt supporting body located under the discharge port and supporting a return route portion of the conveyor belt; a belt inversion mechanism configured to invert the conveyor belt such that the conveyance surface of the conveyor belt passing through the return route belt supporting body faces upward; and wherein the dust accumulated in the header chamber being discharged through the discharge port together with the air falls on the conveyance surface of the return route portion of the conveyor belt.