To provide a bed sheet being mountable on a bed mattress without being deviated or wrinkled while sleeping.

This bed sheet covers over the bed mattress. A string passage bag portion 22 is formed around the whole circumference of an opening edge 21 located at the back face side of the bed mattress, and an elastic fastening member 31 is inserted into the string passage bag portion 22. Elastic string members 25A and 25B having clips 26 at both ends are stretched across the mutually facing long side parts and short side parts of the opening edge part 21 of the sheet and pull the edge portion inward.