Abstract: There is provided a first method of preparing a genome library in which PCR is carried out with the use of genomic DNA of target biological species per se or fragment thereof as a direct template and with the use of random primer or one type of primer of specified sequence so as to effect genome amplification, thereby obtaining a genuine library. There is further provided a second method of preparing a genome library in which genome of target biological species is pretreated and thereafter PCR is carried out with the use of one type of primer of inherent sequence so as to effect genome amplification, thereby obtaining a genome library. In both of the methods, a genome library can be prepared conveniently from a minute amount of sample.