A method of providing a document sharing service based on a messaging service includes: receiving, by a server, a document transmission signal for transmitting a document which is 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 second terminal applications respectively corresponding to members of a second chat group different from the first chat group; obtaining, by the server, a document identifier from the document transmission signal, searching, by the server, a database for a document corresponding to the document identifier, and transmitting, by the server, the document to the second terminal applications; and updating, by the server, shared status information of the document in the database based on a shared status of the document in the second chat group.