The purpose of the present invention is to develop a cucumber fruit mottle mosaic virus vector so as to enable a study of gene function through gene silencing phenomenon in cucurbitaceae plants, which has been difficult to study in the past, and to enable the study in fruits as well through stable expression. Furthermore, the present invention establishes a system that enables expression of a foreign protein in plants, thereby, for the first time, providing a vector applicable to both the gene silencing phenomenon and protein expression in cucurbitaceae plants.