An oxygen measurement device constituting an oxygen measurement system includes a urethral catheter and an oxygen sensor main body. The urethral catheter has a shaft in which a urethral catheter lumen that enables circulation of urine flowed in via a urethral catheter port from inside a bladder is formed; and has a hub in which a urine lumen that is provided at a proximal end of the shaft and communicates with the urethral catheter lumen is formed. The oxygen sensor main body is provided on the hub in a manner capable of being brought into contact with urine circulating in the urine lumen, and detects oxygen in the urine.