To provide a penetration testing machine capable of obtaining only the necessary section of sound information changing in response to a soil property.

The penetration testing machine has a sound detecting means 13 detecting a sound transmitted on a penetration rod 7 penetrated into the ground, amplifies the sound information detected by the detecting means 13 by an amplifying section 16, and transmits the sound information to an arithmetic processing section 15 after the information is processed by a filter in a filter processing section 17. In the arithmetic processing section 15, the transmitted sound information is stored in a storage section 19 when a changeover switch 23 is turned on, and the transmitted sound information is not stored and annulled when the switch 23 is turned off. The switch 23 is on/off operated by the decision of an operator listening to a sound output from an output section 20 to a headphone 22.