The utility model relates to a bag sterilizer (100). The bag sterilizer (100) comprises a shell (10), and a sterilizing lamp (20) and a control circuit assembly (30) which are arranged inside the shell (10), wherein the sterilizing lamp (20) is controlled by the control circuit assembly (30); the shell (10) comprises a lampshade (11), and an accommodating cabin (12) detachably connected with the lampshade (11); the control circuit assembly (30) is arranged inside the accommodating cabin (12); the control circuit assembly (30) comprises a circuit board (35), as well as a power supply (31) and a time controller which are electrically connected with the circuit board (35), and a switch (34); the sterilizing lamp (20) is electrically connected with the circuit board (35) and stretches into the lampshade (11); and the time controller is used for controlling the sterilizing time. The bag sterilizer (100) is simple in structure; and in use, the bag sterilizer (100) automatically stops or starts the sterilizing lamp (20) through the control circuit (30), so that the bag sterilizer (100) is easy to operate.