A bobbin detection mechanism for a bobbin transport device for a roving frame, the bobbin detection mechanism comprising: a plurality of full bobbin hangers (21F, 61F, 80F) for hanging a full bobbin; a plurality of empty bobbin hangers (21E, 61E) for hanging an empty bobbin, the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E) being arranged alternately; and a rail member guiding the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E), each of the full bobbin hangers (21F, 61F, 80F) including: a full bobbin shaft portion hanging down from the rail member; and a full bobbin vertically movable member (49, 69, 81) contactable with a bobbin mounted on the full bobbin shaft portion and movable to a lowest position relative to the full bobbin shaft portion and to a holding position that is higher than the lowest position, the full bobbin being held by one of the full bobbin hangers (21F, 61F, 80F) with an upward movement of the full bobbin vertically movable member (49, 69, 81), characterized in that the bobbin detection mechanism includes: a full bobbin hanger photoelectric sensor including a full bobbin hanger sensor light emitter configured to emit a sensor light (L, L1) in a bobbin hanger arrangement direction in which the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E) are arranged, and a full bobbin hanger sensor light receiver configured to receive the sensor light from the full bobbin hanger sensor light emitter; and a full bobbin hanger sensor light shield (51, 71, 83) formed in the full bobbin hanger vertical movable member (49, 69, 81), and configured to block the sensor light (L, L1) from the full bobbin hanger sensor light emitter, and the sensor light (L, L1) from the full bobbin hanger sensor light emitter is set at such a height where the sensor light (L, L1) is blocked by the full bobbin hanger sensor light shield (51, 71, 83) when the full bobbin vertically movable member (49, 69, 81) is positioned at the holding position. a plurality of full bobbin hangers (21F, 61F, 80F) for hanging a full bobbin; a plurality of empty bobbin hangers (21E, 61E) for hanging an empty bobbin, the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E) being arranged alternately; and a rail member guiding the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E), each of the full bobbin hangers (21F, 61F, 80F) including: a full bobbin shaft portion hanging down from the rail member; and a full bobbin vertically movable member (49, 69, 81) contactable with a bobbin mounted on the full bobbin shaft portion and movable to a lowest position relative to the full bobbin shaft portion and to a holding position that is higher than the lowest position, a full bobbin shaft portion hanging down from the rail member; and a full bobbin vertically movable member (49, 69, 81) contactable with a bobbin mounted on the full bobbin shaft portion and movable to a lowest position relative to the full bobbin shaft portion and to a holding position that is higher than the lowest position, the full bobbin being held by one of the full bobbin hangers (21F, 61F, 80F) with an upward movement of the full bobbin vertically movable member (49, 69, 81), characterized in that the bobbin detection mechanism includes: a full bobbin hanger photoelectric sensor including a full bobbin hanger sensor light emitter configured to emit a sensor light (L, L1) in a bobbin hanger arrangement direction in which the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E) are arranged, and a full bobbin hanger sensor light receiver configured to receive the sensor light from the full bobbin hanger sensor light emitter; and a full bobbin hanger sensor light shield (51, 71, 83) formed in the full bobbin hanger vertical movable member (49, 69, 81), and configured to block the sensor light (L, L1) from the full bobbin hanger sensor light emitter, and a full bobbin hanger photoelectric sensor including a full bobbin hanger sensor light emitter configured to emit a sensor light (L, L1) in a bobbin hanger arrangement direction in which the full bobbin hangers (21F, 61F, 80F) and the empty bobbin hangers (21E, 61E) are arranged, and a full bobbin hanger sensor light receiver configured to receive the sensor light from the full bobbin hanger sensor light emitter; and a full bobbin hanger sensor light shield (51, 71, 83) formed in the full bobbin hanger vertical movable member (49, 69, 81), and configured to block the sensor light (L, L1) from the full bobbin hanger sensor light emitter, and the sensor light (L, L1) from the full bobbin hanger sensor light emitter is set at such a height where the sensor light (L, L1) is blocked by the full bobbin hanger sensor light shield (51, 71, 83) when the full bobbin vertically movable member (49, 69, 81) is positioned at the holding position.