It is identified the new class of invariants which values are constant at change of value of an inde-pendent variable. Their properties and a deriving method are shown on already known and still un-known instances, concerning to various areas of physics. In particular, new invariants (50), (55) and (57) for the straight lines intersected in one point on a plane have been discovered. Besides, the re-quest for detection of the third (not dependent on two already known) an invariant (31) electromag-netic fields for a special case of the special theory of relativity is made.