The invention provides a light-emitting element whose light-emitting efficiency is improved by setting a generation probability of a single excitation state (S1) in a light-emitting layer of the light-emitting element to be above a theoretical value (25%). The light-emitting element has a structure in which a first organic compound and a second organic compound form an exciplex (excited complex) in a light-emitting layer. The S1 level and the T1 level of the formed exciplex are positioned extremely close to each other compared with the S1 level and the T1 level of the respective substances (the first organic compound and the second organic compound) before the formation of the exciplex. Thus, a part of the energy in T1 of the exciplex is easy to be transferred to S1. Thus, the light-emitting element is characterized by obtaining a generation probability higher than the theoretical generation probability (25%), so that the light-emitting efficiency of the light-emitting element using energy from S1 can be improved.