the present invention is characterized in that graphenes are dispersed to a surface and or inside of a nanofiber here the nanofiber has a diameter of 1 u02dc 1000 nm preferably 10 u02dc 500 nm more preferably 100 u02dc 200 nm the nanofiber may be a polymer nanofiber formed of polymers or a carbon nanofiber prepared by carbonizing the polymer nanofiber the graphenes include at least one type of monolayer graphenes and multilayer graphenes having a thickness of 10 nm or less when the multilayer graphenes have a thickness more than 10 nm they are present in the form of a graphite plate implemented as the graphenes are bonded to each other as a result mechanical and electric characteristics of the graphenes can not be prepared for instance when the multilayer graphenes have a thickness more than 10 nm charge mobility is significantly degraded when being applied to a semiconductor device furthermore mechanical strength due to complexity with other materials is significantly degraded in order to produce desired mechanical and electric characteristics of the graphenes the graphenes are preferably oriented aligned parallel to an axis of the nanofiber the reason is as follows when the graphenes are oriented parallel to an axis of the nanofiber an electric characteristic of the graphenes is implemented along the orientation direction and mechanical strength in the orientation direction is significantly increased when the multilayer graphenes have a thickness more than 10 nm it is difficult to implement the orientation characteristic the graphenes dispersed in the nanofiber may be graphene oxides in an oxidized state or.