To solve such a problem that in a dust collecting apparatus equipped on a table-top circular saw, as it is conventionally constituted so that the dust is prevented from flowing reversely by a valve opening/closing by a force of a wind generated by rotation of the circular saw, and when the force of the wind is weak, the valve is not enough opened, there exists a possibility of efficiently collecting the dust, and to thereby always stably collect the dust to prevent the dust from reverse flow.

A reverse flow preventing wall 12 decreasing gradually the flow path area as it reaches on the lee is fixed on a dust collecting opening 9 or its lee side to make stable dust collecting efficiency and preventing the reverse flow compatible.