A monitoring apparatus includes: a monitoring portion that monitors a voltage of each of battery cells connected in series, each of the battery cells having an electrode terminal; and a wiring portion that connects the monitoring portion and the electrode terminal. The wiring portion includes a first flexible substrate and a second substrate that have flexibility and are integrally linked with each other. A linking part where the first flexible substrate and the second flexible substrate are linked is bent. The first flexible substrate is connected with the electrode terminal. The second flexible substrate is connected with the monitoring portion. One of the first flexible substrate and the second flexible substrate includes an arm. Another of the first flexible substrate and the second flexible substrate other than the one including the arm includes a slit. The arm is fixed to the slit, causing the linking part to be reinforced.