A yarn processing apparatus (7, 107, 207) comprising: a yarn processing unit in which yarn running spaces are formed and which is configured to perform a predetermined process for yarns running in the yarn running spaces, the yarn running spaces extending along a yarn running direction and being aligned at predetermined intervals in an arrangement direction intersecting with the yarn running direction; and a yarn placing unit (50, 150) configured to place the yarns in the yarn running spaces, the yarn placing unit (50, 150) including: a first holding unit (24, 224) including first retaining grooves aligned in the arrangement direction; and a second holding unit (25, 125, 225) which is provided downstream of the first holding unit (24, 224) in the yarn running direction and which is configured to hold the yarns while intervals of the yarns held by the first retaining grooves are maintained, the first holding unit (24, 224) being able to take a first yarn threading position where the yarns are threaded to the first holding unit (24, 224) and a first placing completion position which is positioned upstream of the yarn running spaces in the yarn running direction and where placing of the yarns in the yarn running spaces is completed, the second holding unit (25, 125, 225) being able to take a second yarn threading position where the yarns are threaded to the second holding unit (25, 125, 225) and a second placing completion position which is positioned downstream of the yarn running spaces in the yarn running direction and where the placing of the yarns in the yarn running spaces is completed, and the first holding unit (24, 224) at the first yarn threading position being adjacent to the second holding unit (25, 125, 225) at the second yarn threading position in the yarn running direction. a yarn placing unit (50, 150) configured to place the yarns in the yarn running spaces, the yarn placing unit (50, 150) including: a first holding unit (24, 224) including first retaining grooves aligned in the arrangement direction; and a second holding unit (25, 125, 225) which is provided downstream of the first holding unit (24, 224) in the yarn running direction and which is configured to hold the yarns while intervals of the yarns held by the first retaining grooves are maintained, the first holding unit (24, 224) being able to take a first yarn threading position where the yarns are threaded to the first holding unit (24, 224) and a first placing completion position which is positioned upstream of the yarn running spaces in the yarn running direction and where placing of the yarns in the yarn running spaces is completed, the second holding unit (25, 125, 225) being able to take a second yarn threading position where the yarns are threaded to the second holding unit (25, 125, 225) and a second placing completion position which is positioned downstream of the yarn running spaces in the yarn running direction and where the placing of the yarns in the yarn running spaces is completed, and the first holding unit (24, 224) at the first yarn threading position being adjacent to the second holding unit (25, 125, 225) at the second yarn threading position in the yarn running direction. a first holding unit (24, 224) including first retaining grooves aligned in the arrangement direction; and a second holding unit (25, 125, 225) which is provided downstream of the first holding unit (24, 224) in the yarn running direction and which is configured to hold the yarns while intervals of the yarns held by the first retaining grooves are maintained, the first holding unit (24, 224) being able to take a first yarn threading position where the yarns are threaded to the first holding unit (24, 224) and a first placing completion position which is positioned upstream of the yarn running spaces in the yarn running direction and where placing of the yarns in the yarn running spaces is completed, the second holding unit (25, 125, 225) being able to take a second yarn threading position where the yarns are threaded to the second holding unit (25, 125, 225) and a second placing completion position which is positioned downstream of the yarn running spaces in the yarn running direction and where the placing of the yarns in the yarn running spaces is completed, and the first holding unit (24, 224) at the first yarn threading position being adjacent to the second holding unit (25, 125, 225) at the second yarn threading position in the yarn running direction.