A collimator, a radiological imaging apparatus and a nuclear medicine diagnosis apparatus which are able to improve the sensitivity are provided. The radiological imaging apparatus has a collimator 11 disposed to oppose a radiological detection device 12 and having through-holes 11a for passing to the radiological detection device 12 gamma rays in a specified direction out of those radiated from an object to be examined. The collimator 11 is produced by mutually coupling a plurality of metal tubular members 11A each having the through-hole 11a with the help of a bonding agent S in alignment with a plurality of detectors 12a constituting the radiological detection device 12.