Seventy-four-year female patient presented back pain, radiating pain from both posterior thigh and intermittent claudication for two years. Preoperative radiography and MRI demonstrated L2~S1 spinal stenosis. She underwent OLIF and posterior instrumentation L2-S1. At 3 days postoperatively, she presented nausea, abdominal discomfort and showed low SpO2 and drowsy mental state with abrupt vomiting. Abdomen X-ray and CT demonstrated severe paralytic ileus and Chest CT and bronchoscopy demonstrated aspiration pneumonia and ARDS. She transferred to respiratory internal medicine in intensive care unit. She recovered for one month of ICU care and was possible to wheelchair ambulation. Approximately 3.5% of patients undergoing elective spine surgery develop paralytic ileus. Especially, anterior or lateral access spine surgery, gastroesophageal reflux disease and posterior instrumentation have a high risk of ileus. If patients present nausea, vomiting, abdominal discomfort, constipation, doctor must be evaluated paralytic ileus and treat it by NPO, early ambulation, nasogastric tube and possible pharmacological agents.