A medical sheet base includes a polyurethane nonwoven fabric and a polyurethane film combined with each other, and is improved in stretchability, air permeability, moisture permeability, water resistance and flexibility over prior-art medical sheet bases as required of the medical sheet base. The polyurethane nonwoven fabric includes continuous filaments each having an average filament diameter of not greater than 50 μm, the filaments being deposited in a substantially unbound state and partly bonded to each other. The polyurethane film has minute pores present in opposite surfaces thereof and each having a diameter of not greater than 10 μm, and minute pores communicating with each other along the thickness thereof.