A portable working machine has a motive power source for producing a rotational motion, a cutting blade mounted to undergo linear reciprocating motion, and a reduction mechanism for reducing a speed of the rotational motion produced by the motive power source. A motion conversion mechanism converts the rotational motion reduced in speed by the reduction mechanism into a linear reciprocating motion of the cutting blade. A case accommodates therein the reduction mechanism and the motion conversion mechanism and has a lower surface. A cover member covers the lower surface of the case. The cover member has a first part connected to the lower surface of the case and a second part contiguous to the first part and extending to underlie a part of the lower surface of the case located below the reduction mechanism with a space defined between the part of the lower surface of the case and the second part of the cover member. An impact-absorbing member is disposed in the space between the part of the lower surface of the case and the second part of the cover member.