An object is to provide a substrate conveyance apparatus and a substrate detection device capable of improving flexibility in arrangement layout.The substrate detection device includes a projector 41 for projecting inspection light 40 so as to pass through a predetermined position on a path of a substrate 4 conveyed by conveyance belts 26, a light receiver 42 for receiving the inspection light 40 projected by the projector 41, and a detector (a control device 15) for detecting that the substrate 4 reaches the predetermined position based on a decrease in the amount of received light of the inspection light 40 received by the light receiver 42 when the substrate 4 conveyed by the conveyance belts 26 reaches the predetermined position and a portion of the inspection light 40 is blocked by the substrate 4. The inspection light 40 is projected from the projector 41 so as to include opposite ends of a width direction of the conveyance belts 26 in an optical path of the inspection light in a direction orthogonal to a conveyance direction of the substrate 4 conveyed by the conveyance belts 26 and the light receiver 42 receives the inspection light passing through upper and lower regions of the conveyance belts 26 in the width direction.