In view of the above-described problems, the present invention provides the substrate processing apparatus which transfers substrates held in a carrier in a horizontal attitude into and out of the apparatus while processing the substrates in a vertical attitude. Such an apparatus allows a speedy and simple turn of the substrates and suppresses generation of particles. Further, in order to handle the substrates in a vertical attitude, the present invention also provides the substrate transfer apparatus for transferring the substrates held in a carrier in a horizontal attitude into another carrier to be held in a vertical attitude.