To provide a production method of an ingot for manufacturing an Fe-Ni base alloy thin plate for shadow mask, etc., improving uneven etching grade while restraining increase of the manufacturing cost as much as possible.

In the production method of the ingot for manufacturing the Fe-Ni base alloy containing 20-80 mass% Ni and performing the etching treatment, the molten alloy at ≥1500°C is cast into an ingot case. It is desirable that the ingot case is formed flat in the cross sectional shape and the weight ratio of the ingot case to the molten alloy is made to ≥1.1.