Ultrashort-pulse laser-working method and apparatus and structural bodies produced by using the same

A laser-working apparatus, which comprising:

• a splitter for splitting a single pulse laser beam having a time width of not more than 500 picoseconds into plural pulse laser beams;
• a time-delayer for subjecting said plural pulse laser beams to time delaying;
• a beam shape-rectifying optical system for adjusting a working surface-irradiating shape, an intensity distribution and a working surface-irradiating position of each of the plural pulse laser beams;
• and
• a beam-propagating optical system, wherein a target object to be irradiated is worked with the plural laser beams, while the respective working surface-irradiating shapes of said plural laser beams are partially or entirely spatially overlapped with each other or one another, and a time period during which each of the pulse laser beams is irradiated on a working surface of the object is set to a time interval of from a width of a pulse to nanosecond.