In the past, when boiling spinach, it is suggested that one should use boiling water. It is said that this removes the oxalic acid ingredient and other ingredients with a non-taste, and improves the color. In this study the temperature of the boiling water and the influence of the boiling time were evaluated.1) The oxalic acid content decreased when the temperature of the boiling water was high and when the boiling time was long.2) There was no difference in the color of the boiled spinach.3) Even if the boiling time was long at 60 and 70°C, the oxalic acid content and the change in its strength were low and the heating was insufficient.4) At 80°C with a sufficient boiling time, a moderate condition was attained. For the oxalic acid content and softness evaluation, heating was from 2 to 3 minutes at 100°C which was considered moderate in the past.5) At 100°C, the range in the boiling time which can make spinach have a moderate condition was short. From 80 to 90°C, the time period was long. When boiling spinach is always kept in the hot water, boiling is not necessary and it is possible to say that the heating power should be maintained to provide an 80°C temperature or higher.