Recently, view point of service has been widespread. In learning domains, service providers have been required to adopt it and to provide values co-created by teachers and learners. The value co-creation takes place in joint sphere where providers and customers make interaction, and the value is subjectively perceived by receivers (learners in learning service). That is, a mental state of leaner is one of possible value in the co-creation. The current study aims to develop a conceptual framework which describes mental states of learners for specifying values in the co-creation. As a result, we proposed ontological descriptions of learning event which consists of a teacher, a learner, learning materials, and a learning action by the learner. In concrete terms, we proposed ontological descriptions for receiver states in a learning activity, on the basis of a conceptual model of value co-creation. The ontological descriptions are useful for sharing knowledge on values perceived by learners to design learning services.