A waveguide type optical interferometer circuit formed in one plane comprising: an input waveguide; an output waveguide; an optical branching unit connected to the input waveguide; an optical coupling unit connected to the output waveguide; a plurality of optical waveguides having different lengths from each other and being interposed between the optical branching unit and the optical coupling unit; a light intensity compensating region is formed on an optical path extending from the optical branching unit to the optical coupling unit, the light intensity compensating region is provided to the optical branching unit or the optical coupling unit and is formed as at least one groove intersecting with the optical path, and a light intensity coefficient relative to light propagating on a portion of an optical path excluding the light intensity compensating region is different from a light intensity coefficient relative to light propagating on the light intensity compensating region, wherein the light intensity coefficient is a coefficient of change of an optical distance L with respect to a light intensity P, dL/dP; wherein if a total incident light intensity to be made incident on the optical branching unit is defined as Ptotal, a straight line of the optical path joining a center of a connecting end from the input waveguide to a center of a connecting end to the i-th, where i is a positive integer, optical waveguide interposed between the optical branching unit and the optical coupling unit in a case of absence of the light intensity compensating region is defined as K, an optical distance of K is defined as Lai, an optical distance of the i-th optical waveguide is defined as Lbi, a total value of changes in optical distances due to formation of the light intensity compensating region having a groove width of the groove intersected by the optical path of the i-th straight line K is defined as Lri, the waveguide type optical interferometer circuit is characterized in that it satisfies d(2 x Lai + Lbi + Lri)/dPtotal =C, where i = 1 to N, C is a constant value irrespective of the value of i, N is the number of the optical waveguides, and Ptotal is the total incident light intensity. an input waveguide; an output waveguide; an optical branching unit connected to the input waveguide; an optical coupling unit connected to the output waveguide; a plurality of optical waveguides having different lengths from each other and being interposed between the optical branching unit and the optical coupling unit; a light intensity compensating region is formed on an optical path extending from the optical branching unit to the optical coupling unit, the light intensity compensating region is provided to the optical branching unit or the optical coupling unit and is formed as at least one groove intersecting with the optical path, and a light intensity coefficient relative to light propagating on a portion of an optical path excluding the light intensity compensating region is different from a light intensity coefficient relative to light propagating on the light intensity compensating region, wherein the light intensity coefficient is a coefficient of change of an optical distance L with respect to a light intensity P, dL/dP; wherein if a total incident light intensity to be made incident on the optical branching unit is defined as Ptotal, a straight line of the optical path joining a center of a connecting end from the input waveguide to a center of a connecting end to the i-th, where i is a positive integer, optical waveguide interposed between the optical branching unit and the optical coupling unit in a case of absence of the light intensity compensating region is defined as K, an optical distance of K is defined as Lai, an optical distance of the i-th optical waveguide is defined as Lbi, a total value of changes in optical distances due to formation of the light intensity compensating region having a groove width of the groove intersected by the optical path of the i-th straight line K is defined as Lri, the waveguide type optical interferometer circuit is characterized in that it satisfies d(2 x Lai + Lbi + Lri)/dPtotal =C, where i = 1 to N, C is a constant value irrespective of the value of i, N is the number of the optical waveguides, and Ptotal is the total incident light intensity.