The accident took place around 6.30 a.m. on the Mandia by-pass near Pali, some 300 km from here.
The bus carried pilgrims from Utharada village in Salumber tehsil of Udaipur district.
"It was returning from the shrine of Baba Ramdeo, a local deity, near Pokharan in Jaisalmer district, when a truck collided with it head on," Superintendent of Police Jainarayan Sher told IANS over phone.
Of the injured, 18 are critical, Sher added.
A case has been filed against the driver of the bus and the cause of the accident is being investigated, police said.