A coordinate input apparatus having a stable and good input sense irrespective of different input conditions such as a vibration input position, a pen pressure and a pen angle. The coordinate input apparatus acquires an input coordinate in accordance with a delay time required for vibration input from a vibration input pen to a vibration propagation plate to reach a vibration sensor. A controller of the apparatus drives the vibration input pen at a first drive level. A window signal generator of the apparatus generates a window signal indicating that a significant signal was detected, when the level of an envelope detected from a signal supplied from the vibration sensor exceeds a detection threshold value. In accordance with the window signal, delay times tp and tg are acquired. A level discriminator of the apparatus judges whether the level of the envelope exceeds a discrimination threshold value. If it is judged that the level exceeds the discrimination threshold value, the controller drives the vibration input pen at a second drive level lower than the first drive level to acquire the delay times tp and tg.