PURPOSE: To add an adding material by appropriate quantities in accordance with a main and adding material by putting a plug body having a diameter smaller then a material throwing-in port formed through the cap body of the title cooking container in the port in a removable state.

CONSTITUTION: A transparent cap body 11 which is made of a synthetic resin and caps the upper opening of this cooking container 5 has a recessed housing section 12 which is used for housing an adding material and becomes gradually deeper toward the outer periphery of the cap body 11, with an adding material throwing-in port 13 through which an adding material is poured into the container 5 near its inside wall being formed at the deepest part of the housing section 12. A plug body 16 which is put in the port 13 in a removable state is provided with a hole 17, the diameter of which is set so that the optimum quantity of salad oil can be allowed to drop through the hole at the time of producing mayonnaise. In other words, a prescribed quantity of salad oil is put in the section 12 and the salad oil is mixed with the material in the container by allowing the salad oil to drop into the container 5 from the hole 17 of the plug body 16. The salad oil drops from the hole 17 by fixed quantities at the optimum speed for producing mayonnaise and is mixed with the material in the container 5, resulting in mayonnaise.