PROBLEM TO BE SOLVED: To provide an insect pest controlling agent higher in pest controlling effect and high in stability by using a laver extract and a manufacturing method therefor.SOLUTION: Water such as purified water is input into a predetermined container and organic acid is input into the container so that the content becomes the above mentioned content and mixed (Step S2 and S3). High molecule porphyran having a molecular weight of 30,000 Da or more is input into a solution in the container so that the content becomes a predetermined content (Step S4) and stirred well, an emulsifier is input so that the content becomes a predetermined content (Step S5) and stirred efficiently and mixed. Meanwhile, oil is fractionated so that the content becomes a predetermined content (Step S6), a high molecule porphyran solution to which the emulsifier is mixed is sufficiently stirred and the high molecule porphyran solution and plant oil are sufficiently emulsified by inputting oil of the appropriate amount into the
