The explosion took place last night when huge number of people were at the shrine for a ritual ceremony.
A large number of women and children are among the casualties.
Devotees, from across the country, frequently visit the shrine on Thursdays as it is a popular day to visit Sufi shrines.
Daesh terrorist group has claimed responsibility of the deadly attack but the government and the army still claim that the Daesh has no organized presence in Pakistan.
The government has indirectly accused India and Afghanistan for the deadly attack. Pakistan believes terrorist who have targeted different parts in Pakistan in recent days, have their sanctuaries in Afghanistan.
A nationwide security crackdown has also been launched on Friday in which at least 35 terrorists were killed.
Prime Minister Muhammad Nawaz Sharif has expressed sorrow and grief over the blast. In his statement, he said such incidents cannot deter the resolve of the nation to defeat common enemies.
Pakistan Chief of Army Staff General Qamar Javed Bajwa has promised strong retaliation against terrorists in the country.
The bombing at Qalandar's shrine was at least the 7th militant attack over the past five days in Pakistan.