The body of the woman was pulled from the rubble of the 21-apartment building in a built-up central area of the southern coastal town on the island of Tenerife, the islands' emergency services said in a tweet.
Earlier, a National Police spokesman said three people suffered injuries but it was not known how many people were in the building when it collapsed, sending a dust cloud into the air.
Witnesses told Spanish media they heard a loud bang before the collapse. They said the building had been undergoing renovations.
The officer, who spoke on condition of anonymity in keeping with police regulations, said the cause of the collapse was not known but was being investigated.