Granulomonocytapheresis (GMA) is an effective treatment for inducing remission in patients with refractory ulcerative colitis (UC). Furthermore, GMA has very few side effects and can be performed without using drugs except anticoagulants. However, GMA is sometimes challenging to perform, especially in children, as it usually requires securing two blood vessels. We attempted GMA by the single-needle method in a girl with UC, which is performed by securing only one blood vessel. In the present case, GMA could be performed 10 times without any side effects. Our case shows that GMA with the single-needle method was feasible in children with UC.