Sensor apparatus

A sensor apparatus, comprising:

• a casing in which a first opening and a second opening are formed;
• a first flow channel formed in the casing and that communicates with the first opening and the second opening to form a flow of fluid from the first opening to the second opening;
• a pressure changer formed in the first flow channel and that is configured to change the pressure of the fluid flowing through the first flow channel;
• a second flow channel which branches from the first flow channel on an upstream side relative to the pressure changer;
• and
• a third flow channel which communicates with the second flow channel and in which a detector of a sensor chip is arranged, wherein
• the first flow channel includes a curved portion forming an arc as viewed in a first direction, the curved portion being formed upstream of the pressure changer,
• in a cross section crossing the first direction, the curved portion includes a first surface and a second surface which face each other in a direction along a radius of curvature of the curved portion,
• the second surface is disposed closer to a center of curvature of the curved portion as compared with the first surface, and
• a third opening is formed in the second surface as a connection portion connecting the first flow channel and the second flow channel.