A portable working machine includes a working machine body, bolt members erected on the working machine body, a cover member configured to be attachable to and detachable from the working machine body, in which the cover member has through-holes through which the bolt members are inserted when attaching the cover member, fixing members configured to be fastened to the bolt members to fix the cover member attached to the working machine body, and a holding member attached to an outer surface of the cover member with a predetermined gap space between the holding member and the outer surface of the cover member, in which the holding member is configured to retain the fixing members on an outer side of the outer surface of the cover member when a fastening of the fixing members to the bolt members is released to prevent the fixing members from dropping off the cover member.