Cast-in object plate member, partition plate for intake port, intake-port forming sand core and cylinder head

A partition plate (100) (cast-in object plate member) is preliminarily set in an intake-port forming sand core (200), by which an intake port (14) of a cylinder head (10) is molded, and cast in during cast molding of the cylinder head for partitioning the intake port. The partition plate has both distal ends (Ta,Tb), spaced apart in a longitudinal direction, one of which corresponds to an intake-side distal end at which an acute-angled end face (150) is formed to induce core breaking in a port core at an area closer to the intake-side distal end (Tb).