PURPOSE: To prevent the reliability from lowering after long term use while making mass production possible by bonding a silicon substrate to a glass substrate on which a channel is formed and then forming a heater for detecting the flow rate of fluid thereon.

CONSTITUTION: An elongated hole 22 is made, as a channel for fluid, through a glass substrate 21 by ultrasonic machining or laser machining. A silicon substrate 23 is bonded by anodic bonding, for example, to the upper face of the substrate 21 while covering the elongated hole 22 on one opening side thereof. An insulating layer of oxide film, for example, is formed on the upper face of the substrate 23 and heaters 25, 26 for detecting the flow rate of fluid are formed thereon of a metal having high temperature coefficient of resistance, e.g. platinum or nickel. The heaters 25, 26 are formed integrally and lead wires are extended from the intermediate and end parts thereof with bonding pads 30, 31, 32 being formed at the tips thereof. Since the mass flow sensors can be manufactured by batch process using semiconductor fabrication technology or micromachining technology, the mass flow sensors can be mass-produced.