Embodiments of the invention provide a magnetic disk drive which has improved electrical properties owing to a reduction in the loss of transmission line, improved vibration properties owing to a reduction in the stiffness of wiring around the head, and a flat impedance in the transmission line. In one embodiment, a magnetic disk drive comprises a suspension; a magnetic head coupled with the suspension and configured to write and read information to and from a magnetic recording medium; and a transmission line disposed on the suspension to transmit writing and reading information to and from the magnetic head. The transmission line includes a writing line and a reading line, a lower conductor disposed underneath the writing line and the reading line, and an insulating layer interposed between the lower conductor and the writing and reading lines. The lower conductor comprises copper or copper-based alloy and has a thickness of substantially less than 25 .mu.m, desirably about 2-12 .mu.m, and more desirably about 5 .mu.m.