In Japan, leukocytapheresis (LCAP) therapy has been carried out for ulcerative colitis as an effective therapy with a low incidence of side-effects. In the present study, we serially investigated the influence of LCAP therapy on anemia and hemodynamics in patients with ulcerative colitis using a non-invasive method with a Crit-Line monitor (CLM) (Hema Metrics Inc., Salt Lake City, UT and Boston, MA, USA). We carried out LCAP on 10 patients with ulcerative colitis using a CS-100 Cellsorba EX LCAP filter in 34 courses of LCAP. The mean hematocrit value, which was measured using the Crit-Line monitor, was 21.8 ± 0.2% (21.0–22.4%), which showed no significant changes after each LCAP therapy. The actual erythrocyte count, hemoglobin and hematocrit values decreased by 244 000/mm3, 0.7 g/dL and 2.1%, respectively, however, the differences were insignificant. These values corresponded to 7.8, 8.0 and 7.6% of the values before LCAP, respectively. There were no significant changes in systolic blood pressure, diastolic blood pressure, or heart rate during LCAP. The results of this study suggest that one course of LCAP does not exacerbate anemia, and it does not influence hemodynamics. However, considering the exacerbation of anemia in patients with severe ulcerative colitis caused by massive melena, monitoring with a less invasive Crit-Line monitor and a vital information monitor might be useful.