Optical waveguide element, optical modulator using optical waveguide element, and optical transmission device

The purpose of the present invention is to provide an optical waveguide element in which the positional relationship between an optical waveguide substrate and a reinforcing member can be appropriately set. This optical waveguide element is provided with an optical waveguide substrate (11) that is provided with an optical waveguide (10), and a reinforcing member (2) that is disposed above the optical waveguide in the vicinity of the end of the optical waveguide, the optical waveguide substrate and the reinforcing member being joined via an adhesive layer (3). Spacers (SP1, SP2) are disposed between the optical waveguide substrate and the reinforcing member so as to sandwich the optical waveguide. 本发明的目的在于提供一种能够适当地设定光波导基板与加强部件的位置关系的光波导元件。光波导元件具备光波导基板（11）和加强部件（2），该光波导基板（11）具备光波导（10），该加强部件（2）在该光波导的端部附近配置于该光波导的上侧，该光波导基板和该加强部件经由粘接层（3）而接合，其特征在于，在该光波导基板与该加强部件之间以夹着该光波导的方式配置有间隔件（SP1、SP2）。