To provide a component storage case capable of allowing a user to efficiently carry an attachment component which is attached to an electric power tool.

A component storage case 20A1 (20A2) stores an attachment component which is attached to an electric power tool having a battery holding part capable of holding a battery and may be held at the battery holing part. The component storage case includes a pair of rails 22B1, 22B2 which may engage with the battery holding part. Additionally, the component storage case may be stored in a storage part of the battery which is provided at a power tool storage case for storing the electric power tool.