The 28-year-old died after the part of a balcony in the Madrid neighbourhood of Argüelles collapsed, falling on him.
His 27-year-old friend received only a fractured left hand in the incident at around 10pm on Wednesday, Spain's 20 minutos reported.
The two men had just ordered the bill and were preparing to leave when part of the balcony above them gave way, owners told the daily.
One of the waitresses suffered a panic attack after seeing one of the men "with his head split open", witnesses said.
The man with serious injuries was rushed to hospital but could not be saved.
Neighbours and residents said there had been no indication the balcony had been in a poor state of repair.