A chat service providing apparatus may include a message analyzer and an artificial intelligence processor. The message analyzer may identify a first expression item included in at least one chat message received from a user terminal, analyze an attribute allocated to the first expression item on the basis of an analysis medium frame, and determine a user's intention according to a result of analyzing the attribute. The artificial intelligence processor may recommend a second expression item from among a plurality of registered expression items on the basis of a conversion condition which is an algorithm for selecting an expression item having an attribute corresponding to the user's intention among the plurality of expression items. The analysis medium frame may include, as an attribute, at least one of a description of an expression item, a reference emoji, a representative intension, and a representative language.