She plunged down the shaft at a branch on High Street in Solihull and had to be rescued by firefighters.
The woman, who is said to be in her 20s, is now being treated in the trauma centre at Queen Elizabeth Hospital in Birmingham.
Her injuries are not believed to be life-threatening, West Midlands Ambulance Service said.
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A spokesman said: "Ambulance staff were told that the woman in her 20s had tried to use the lift but when she stepped into the lift shaft there was nothing there and she fell approximately 25ft to the bottom of the shaft.
"Ambulance staff worked with firefighters to extricate her from the confined space."
The Starbucks coffee branch will remain closed until an investigation into how the incident happened is completed.
A spokesman said they were "shocked and distressed by this terrible incident", adding they were "working closely" with authorities.
The Health and Safety Executive said it was a matter for the local authority and not them.
Solihull Council said it has a member of staff at the scene.
A woman has broken her pelvis and her legs in a 25ft (7.6m) fall down a lift shaft in a Starbucks coffee shop.