The 25-year-old has joined for the Segunda Division club after scoring 13 goals in 39 appearances last season at Tynecastle.
Head coach Robbie Neilson told the Hearts website: "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."
Juanma had joined the Scottish Premiership outfit after leaving Greek Superleague club Kalloni last year.
"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," added Neilson.
"Hopefully this will enable him to get plenty of game time under his belt over the course of the season."
Spanish striker Juanma has moved to his homeland to sign for Murcia on a season-long loan from Hearts.