Japan has one of the lowest crime rates in the world, but an increasing number of them are committed by older people, the report revealed.
Last year 48,605 elderly people were arrested or investigated for crimes other than traffic offences, a four-fold jump from a decade ago and the highest figure since comparable records began in 1986, the justice ministry said.
"We cannot overlook the possibility of a further rise in crimes by elderly people in the future," the report said, noting crimes by "pre-seniors" aged 50-64, including baby boomers, were also markedly increasing.
"Many of them are isolated from relatives, leading economically unstable lives alone, and have mental and physical problems," the report said.
The number of Japanese aged 65 and over is expected to double over the next two decades, but crimes by the elderly are increasing at a much faster pace.
Seniors accounted for 13.3 percent of offenders in 2007, up sharply from just 2.5 percent in 1988. Over the same period the percentage of elderly people in the population nearly doubled to 21.5 percent.
Meanwhile the total number of crimes recorded over the period - excluding traffic offences - dropped 8.1 percent.
Nearly two-thirds of crimes by the elderly last year were thefts, but the proportion of murders committed by seniors rose 40 percent over the last two decades.
Many seniors who were arrested for the first time in their life suddenly turned to crime for reasons including a "feeling that their pride was hurt," the report said.
Elderly people with previous records of serving time showed a tendency to commit crimes out of economic anxiety and apathy in life, it said.
A study of 50 murder cases by seniors showed the victims were relatives of the offenders in 28 cases. In the case of the nine female offenders, all the victims were relatives.
Frequent excuses for killing relatives were "pessimism for their future" and "fatigue" in caring for them.
"Killing relatives due to fatigue giving care in the aging society is considered one factor that raised the number of homicides by the elderly," the report said.