The shoes have a small generator attached to water-filled soles. Each step puts pressure on the soles, causing the water to spin a small turbine and generate power, NTT said.
The futuristic shoes currently generate 1.2 watts of electricity, "a level sufficient to run an iPod mobile music player forever, as long as the wearer keeps walking," said spokesman Hideomi Tenma.
"The company is trying to improve the power-generating capacity to 3 watts, which is the amount of electricity to power a mobile phone," he said.
"The shoes do not have a power-storage function, but you would be able to charge a mobile phone automatically or talk on it forever as long as you connect the phone to your shoes and just keep walking."
NTT hopes to put the generator into actual products as early as 2010.