The ghastly mishap took place at Trishulia Ghat, a hilly patch on the Ambaji-Danta road near Ambaji town of Banaskantha district.
The private luxury bus, carrying around 70 passengers, overturned at Trishulia Ghat after the driver lost control of the vehicle due to heavy rain in the area.
PM Narendra Modi tweeted condolences at the loss of lives.
He said “I am extremely pained by the loss of lives due to an accident. In this hour of grief, my thoughts are with the bereaved families.