The Spaniard was Hearts’ top scorer last season with 13 league and cup goals but has since dropped out of the first team picture.
New signings Conor Sammon, Tony Watt, Bjorn Johnsen and Robbie Muirhead are all ahead of him in the pecking order and Juanma has not featured for Hearts this season.
A proposed move to the Belgian side Waasland-Beveren fell through and the forward will now return to his homeland.
Tynecastle head coach Robbie Neilson told the club’s website: “We have brought in a number of strikers over the course of the summer months, so needless to say there is a great deal of competition up front.
“Juanma has expressed a desire to play regular first team football, so we decided a loan move would be the best solution for both parties.
“Hopefully this will enable him to get plenty of game time under his belt over the course of the season.”
Juanma, 25, joined Hearts last season from the Greek side Kalloni.