An apparatus for providing a document sharing service based on a messaging service. The apparatus includes a memory configured to store computer readable instructions and a processor configured to execute the computer readable instructions. The processor is configured to execute the computer readable instructions to receive a document transmission signal for transmitting a document displayed in a chat window of a first chat group from a first terminal application corresponding to a member of the first chat group, to a second chat group via second terminal applications respectively corresponding to members of the second chat group, the second chat group being different from the first chat group, obtain a document identifier from the document transmission signal, retrieve a document corresponding to the document identifier, transmit the document to the second terminal applications, and update shared status information of the document in the database based on a shared status of the document in the second chat group. The shared status information includes at least one of a number of users who read the document, and a number of chat groups to which the document is transmitted.