A fallboard structure of a keyboard instrument including an instrument body, a keybed having side portions and provided in the instrument body, and a keyboard section having a rear portion (KBa) and provided in the instrument body, the fallboard structure comprising: a pair of left and right supporting portions (23, 22) fixed to the keybed of the instrument body and respectively disposed at the side portions of the keybed; a fallboard capable of being selectively made in a closed state and an open state, said fallboard covering the keyboard section when it is in the closed state and permitting the keyboard section to be operated for performance when it is in the open state; a front plate having side portions and at least one pivot shaft and having a width thereof at least equal to that of the keyboard section, said front plate being capable of having at least a half-open state of posture and a fully open state of posture, said front plate having supporting means for supporting said fallboard so as to be pivotable around said pivot shaft in opening and closing directions and to have at least said half-open and said fully open states of posture, and shielding a space upward of the rear portion of the keyboard section against a player when it is in the half-open state of posture; a pair of left and right engaging portions provided at the side portions of said front plate; and a pair of left and right displacement guides provided in inner sides of respective ones of said supporting portions so as to correspond to said engaging portions; wherein when said fallboard is made in the open state and each of said engaging portions of said front plate is caused to move along a corresponding one of the displacement guides, said front plate is caused to move in unison with said fallboard and changed over from the half-open state of posture to the fully open state of posture, whereby the space upward of the rear portion of the keyboard section is made open toward the player characterized in that said half-open state of posture allows operations for performance to be carried out with an acoustic piano-like appearance, and said fully open state of posture allows operations for electronic instrument-oriented performance to be carried out. a pair of left and right supporting portions (23, 22) fixed to the keybed of the instrument body and respectively disposed at the side portions of the keybed; a fallboard capable of being selectively made in a closed state and an open state, said fallboard covering the keyboard section when it is in the closed state and permitting the keyboard section to be operated for performance when it is in the open state; a front plate having side portions and at least one pivot shaft and having a width thereof at least equal to that of the keyboard section, said front plate being capable of having at least a half-open state of posture and a fully open state of posture, said front plate having supporting means for supporting said fallboard so as to be pivotable around said pivot shaft in opening and closing directions and to have at least said half-open and said fully open states of posture, and shielding a space upward of the rear portion of the keyboard section against a player when it is in the half-open state of posture; a pair of left and right engaging portions provided at the side portions of said front plate; and a pair of left and right displacement guides provided in inner sides of respective ones of said supporting portions so as to correspond to said engaging portions; wherein when said fallboard is made in the open state and each of said engaging portions of said front plate is caused to move along a corresponding one of the displacement guides, said front plate is caused to move in unison with said fallboard and changed over from the half-open state of posture to the fully open state of posture, whereby the space upward of the rear portion of the keyboard section is made open toward the player characterized in that said half-open state of posture allows operations for performance to be carried out with an acoustic piano-like appearance, and said fully open state of posture allows operations for electronic instrument-oriented performance to be carried out.