Finance minister Sadakazu Tanigaki said: "Japan is eyeing limiting transfers of financial assets and will work hard so that we can start it as soon as possible.
"We have already started the work to specify what would become the targets of rules to limit the transfer of financial assets."
Shinzo Abe, the chief cabinet secretary, said Japan would co-ordinate with the international community on the expected sanctions.
The statements confirm Japanese media reports on Monday that Tokyo was preparing to take action.
The main ferry link and charter flights from North Korea have been suspended indefinitely, and visits by North Korean diplomats have already been banned by Japan after the test-firing of seven missiles on July 5.
Japan lobbied for a UN resolution, which was passed on Saturday, banning the buying and selling of material and technology that could boost North Korea's missile programme.
Japan is one of the strongest critics of North Korea. It is particularly sensitive as Pyongyang's previous test of a long-range missile, the Taepodong-1, flew over Japan into the Pacific Ocean in 1998.