The object is to provide a technique for modifying a bacterium belonging to the genus Kocuria through genetic engineering for industrially effectively utilizing the bacterium belonging to the genus Kocuria. The above object can be achieved by providing a cyclic plasmid, which has a replication region comprising the base sequence of a DNA-binding protein-like protein gene, the base sequence of a replicase-like protein gene, and the base sequence represented by SEQ ID NO:45, and is autonomously replicable in bacteria. As an example of the aforesaid plasmid, a plasmid containing a base sequence represented by SEQ ID NO:3 or 4 which originates in Kocuria sp. MBE131 strain (FERM P-21885) can be cited.