noun
labor contract; employment contract
Refers to the written document itself, as opposed to the abstract agreement (労働契約).
入社時に労働契約書を交わした。
I signed a labor contract when I joined the company.
労働契約 is the abstract labor agreement or contract, while 労働契約書 is the physical or digital document that records it.
Compound of 労働 (labor) + 契約 (contract) + 書 (document).