a composite optical element comprising a faraday rotator , a first and a second birefringent regions , and a fifth region , all said three regions being joined to one plane of said rotator , and a third and a fourth birefringent regions , and a six region , all said three regions being joined to the opposite plane of said rotator , the light that has been transmitted through the first birefringent region passing through the third birefringent region , the light that has been transmitted through the second birefringent region passing through the fourth birefringent region , the optical axis of the first birefringent region and that of the second birefringent region intersecting orthogonally , the optical axis of the third birefringent region and that of the fourth birefringent region intersecting orthogonally , the principal planes of both the first and second birefringent regions having the same ground surfaces , the principal planes of both the third and fourth birefringent regions having the same ground surfaces , the first , second , third , and fourth birefringent regions being of the same material , and the percentage of travel of the light beam through the fifth and six regions being no more than 10 %. a process for producing a composite optical element which comprises joining a plurality of a first birefringent plates and a plurality of a second birefringent plates alternately with adhesive to form a laminate , meanwhile joining numbers of third and fourth birefringent plates alternately with adhesive to form a laminate , cutting the laminates into pieces each of which is the composite optical element of claim 1 , the joints formed using the adhesive constituting a fifth and a sixth regions .