The developement of insecticidal soaps made by various fatty acids and organic control for insect by using of insecticidal soap(fatty acid salts) were empolyed. And the results were as follows: 1. To determine the input volume of potassium hydroxide for saponification of fatty acids, there were compared to individual acid value of fatty acids. in case of coconut fatty acids for saponification was 266.3 mg of potassium hydroxide(266g/1kg of fatty acid) was calculated. 2. To make the 25% soap content by coconut fatty acids, there was required for the 266g of potassium hydroxide and 3,459 liter of soft water. Then the liquor of soap was 4,644 liter. 3. The progress of insecticidal soap made by fatty acids was accomplished indirect heating and stirring reactor (1)to make the volume of potassium hydroxide solution and warming up(90℃) (2)input volume of individual fatty acid (3)more than 30 min stirring reaction (4)cooling progress. 4. Insecticidal value of insecticidal soap was observed more than 92% the dilution of 50 dilution solution in consecutive 5 days of 2 treatments of the 25% soap made by coconut fatty acids on the red pepper. And insecticidal value of insecticidal soap was observed more than 94% the 100 dilution solution in consecutive 5 days of 3 treatments of the 25% soap made by coconut fatty acids on red pepper and cabbage. 5. The treatment of two times of 25% soap made by coconut fatty acids at the 50 dilution solution and 100 dilution solution in spider mite on red bean has 100% insecticidal value. 6. There was no observation phytotoxic sypmtons on red pepper in field, except for 25% soap made by carprylic acid. 7. Over the two times over 0.1% in addition of isopropyl alcohol was to improvement the insecticidal effect, but there was no effect in addition of diatomaceous earth.