Thermal flowmeter

A thermal flowmeter for measuring a flow of a measurement object gas flowing in a main passage, the thermal flowmeter comprising:

• a sub-passage taking a part of the measurement object gas flowing in the main passage;
• a flow measurement element that measures a flow amount of the measurement object gas flowing in the sub-passage;
• a curved passage that is formed in the sub-passage which is bent toward the flow measurement element so that the measurement object gas taken from the main passage flows to the flow measurement element;
• and
• a resistance portion that causes a pressure loss of the measurement object gas flowing at an outer peripheral side of the curved passage becomes higher than that of an inner peripheral side of the curved passage, wherein the resistance portion includes:
• a pair of opposite inclined faces formed on an outer peripheral wall face of the outer peripheral side of the curved passage along a flow direction of the measurement object gas, wherein each of the pair of inclined faces are inclined with respect to a virtual plane following a measurement front face of the flow measurement element to form a concave surface on the outer peripheral wall face, and
• a gap between the pair of opposite inclined faces located at an intersection of the intersection of the opposite inclined faces.