The toilet seat sheet includes a sheet body, an opening formed at a central section of the sheet body, and a separation portion configured to be separated from an inner edge of the opening. The separation portion includes a breaking connection that connects the separation portion to the sheet body, the breaking connection being arranged on a right obliquely rear side and/or a left obliquely rear side of the inner edge of the opening. Further, a rear side edge of the separation portion 3 includes a right side outwardly curved section 321 that protrudes right obliquely rearward and a left side outwardly curved section 322 that protrudes left obliquely rearward. The right side outwardly curved section 321 and the left side outwardly curved section 322 are arranged side by side.