The main objective is to examine whether the severity of peripheral arterial disease (PAD) affects the expenses and hospital stay of the patients who undergo bypass surgery below the inguinal ligament for PAD. Eighty consecutive patients who underwent infrainguinal bypass surgery for PAD between January 2012 and December 2014 were included in the study. Patients were divided into groups according to their critical limb ischemia (CLI) symptoms and the Wound, Ischemia, and Foot Infection (WIfI) classification. As endpoints, we assessed the duration of postoperative hospital stay and expenses during hospitalization. CLI was a significant factor for longer hospital stay and increased medical expenses (p = 0.009 and p = 0.001). In the patients with CLI, significant factors for longer hospital stay and increased medical expenses were (1) history of distal bypass (p = 0.33 and p = 0.003, respectively) and stage 4 local lower limb status in WIfI classification (p = 0.0007 and p = 0.053). PAD severity was associated with prolonged postoperative hospital stay and increased medical expenses. The presence or absence of CLI and its severity according to the WIfI classification correlated with medical expenses and hospital stay duration between the milder and severe groups.