A stepless fastening device, comprising: a cap having a driving gear connected to an underside of the cap and multiple one-direction teeth located around the driving gear; an operation unit located beneath the cap; a base having a spool which has teeth engaged with the driving gear of the cap, and the operation unit being rotatable in a first direction to rotate the spool for tightening a shoelace, the operation unit being rotatable in a second direction to let the spool rotate for loosening the shoelace; whereby the operation unit includes an operation ring, an activation ring and an engaging member; the operation ring of the operation unit includes multiple pressing blocks located on an underside thereof; the activation ring includes a skirt, multiple notches and multiple protrusions, wherein the skirt extends from an underside of the activation ring and the multiple notches are defined in an outer periphery of the activation ring, wherein the protrusions extend from a top of the activation ring and each of them being in contact with one of the pressing blocks, and wherein the activation ring is located in the operation ring, characterized in that the cap includes multiple arms extending from an outer periphery thereof, wherein said arms of the cap are extending through the notches of the activation ring, each pressing block includes an inclined surface, wherein the inclined surface contacts the protrusions of the activation ring, the operation ring of the operation unit is mounted to the arms and is connected to the underside of the cap, wherein, when the operation ring is rotated in the second direction, the operation ring pushes the activation ring away from the cap, wherein the engaging member includes inclined teeth and the engaging member is pushed by the activation ring so that the inclined teeth are disengaged from the one-direction teeth of the cap. a cap having a driving gear connected to an underside of the cap and multiple one-direction teeth located around the driving gear; an operation unit located beneath the cap; a base having a spool which has teeth engaged with the driving gear of the cap, and the operation unit being rotatable in a first direction to rotate the spool for tightening a shoelace, the operation unit being rotatable in a second direction to let the spool rotate for loosening the shoelace; whereby the operation unit includes an operation ring, an activation ring and an engaging member; the operation ring of the operation unit includes multiple pressing blocks located on an underside thereof; the activation ring includes a skirt, multiple notches and multiple protrusions, wherein the skirt extends from an underside of the activation ring and the multiple notches are defined in an outer periphery of the activation ring, wherein the protrusions extend from a top of the activation ring and each of them being in contact with one of the pressing blocks, and wherein the activation ring is located in the operation ring, characterized in that the cap includes multiple arms extending from an outer periphery thereof, wherein said arms of the cap are extending through the notches of the activation ring, each pressing block includes an inclined surface, wherein the inclined surface contacts the protrusions of the activation ring, the operation ring of the operation unit is mounted to the arms and is connected to the underside of the cap, wherein, when the operation ring is rotated in the second direction, the operation ring pushes the activation ring away from the cap, wherein the engaging member includes inclined teeth and the engaging member is pushed by the activation ring so that the inclined teeth are disengaged from the one-direction teeth of the cap.