It is reported by El Pais with reference to the royal court.
It is specified that the day before he had slight symptoms of the disease, after which he passed the test for COVID-19, which showed a positive result.
He will be in quarantine for seven days.
In general, his condition is described as "good".
Queen Letizia and the youngest daughter of the kings, Infanta Sophia, have no symptoms of the disease.
Earlier, Queen Margrethe II of Denmark contracted the coronavirus.
At the same time, on the morning of February 9, it became known that 38-year-old Japanese Princess Yoko from the imperial family, who had previously contracted a coronavirus infection, was diagnosed with pneumonia.