This study consists of Screening Phase, Observation Phase, Treatment Phase, Extension Phase, and Follow-up Phase. Screening assessments will be performed between 42 to 2 days before study drug administration. Observation Phase assessments will be performed a day before or on a day of the initial administration to confirm the eligibility of subjects. The eligible subjects will receive the repeated intravenous administration of E6011. E6011 will be dissolved in physiological saline (nearly 100 mL) for approximately 30-minute infusion. During the Treatment Phase, for the first and second cohorts, E6011 will be administered every 2 weeks up to Week 10, a total of 6 times (with a double dose at Week 0). For the third and fourth cohorts, E6011 will be administered at Weeks 0, 1 and 2, then every 2 weeks up to Week 10, a total of 7 times. Under no safety concerns, Crohn's Disease Activity (CDAI) is less than 150 or a decrease in CDAI from the Observation Phase is greater than 70 and a subject intends to continue administrations, the subject will receive a total of 20 subsequent biweekly administrations (40 weeks) at stable dose (Extension Phase). Subjects will be hospitalized for 24 hours after the initial and second administrations for postdose monitoring and will have out-patient monitoring until 12 weeks after the initial administration. If hospitalization is difficult after the second administration, the subjects can be held at the hospital for 6 hours and then allowed to go home after confirmation of the safety. Subjects who roll over onto the Extension Phase will have continued monitoring until 52 weeks after the initial administration. When the subjects complete (Week 12 or Week 52) or discontinue the study, they will undergo an on-site follow-up 28 days after the study completion or discontinuation and an off-site follow-up or telephone interview 70 days after the final administration. The investigator will conduct full assessments of subjects safety next day of the second administration (24 hours after the second administration) to confirm presence of absence of study-related manifestations which may affect the study drug administration of next cohort. When the sponsor is informed of investigator's judgment on the sixth subject in each cohort, the appropriateness of next cohort will be judged based on the safety data available including the judgment of individual investigator on the next day of the second administration.