The airports nearest to Andorra from Spain are in La Seu d’Urgell, Barcelona, Lleida, Reus and Girona.
From France are in Toulouse, Carcassonne and Perpignan.
Reus airport is 189 km from Andorra on the C-14.
Check out the services at this airport.
Access the list of airports and the bus lines to the country. This link will also provide you with other services that might be of interest to you.