PURPOSE: To obtain the subject repelling solution by emulsifying a mustard oil, a natural material, with a natural material or a surfactant containing a large amount of a natural material and suppressing volatilization of a sharp component.

CONSTITUTION: A mixture comprising a mustard oil as a main liquid and a surfactant such as glue plant formed from a seaweed is blended with water in a ratio of about 1:300-1,000 by weight to give a repelling solution. A gelation solution or a detergent may be used as the surfactant besides the glue plant. An ultrasonic vibrator is used when the mustard oil is mixed with the glue plant solution, numerous foams are generated by resonant action of the ultrasonic vibration, numerous particles of glue plant are attached to the circumference of mustard oil particles to emulsify the mustard oil and to suppress emission of a sharp smell by the particles of glue plant attached to the circumference of the mustard oil. Larvae of green caterpillar, cabbage armyworm and diamondback moth attaching to leaves of cabbage and Japanese radish and larvae of butterflies belonging to the family Lycaenidae, larvae of butterflies belonging to the family Hesperiidae, etc., attaching to flowers of beans can be repelled.