NOVELTY - An indoline derivative (I) is new.    USE - New indoline derivative is used for organic electroluminescent device for electronic device e.g. organic solar cell, organic photoconductor, organic transistor and monochromatic or white illumination device (all claimed).    ADVANTAGE - The organic electroluminescent device containing the indoline derivative has high luminous efficiency and stability. The electronic device provided with the organic electroluminescent device has excellent reliability and durability.    DETAILED DESCRIPTION - An indoline derivative of formula (I) is new.    ring A=group of formula (i) or (ii);    X=O, S, NR11, CR12R13 or SiR14R15;    Y'=O, NR16, CR17R18 or SiR19R20;    R11-R20=H, 1-50C alkyl (optionally substituted by group (C')), 6-60C aryl (optionally substituted by group (A)), fluorenyl (optionally substituted by group (D')), 2-60C heterocyclyl and optionally substituted by group (B'), or -L1-N(Ar3)(Ar4);    R1-R4=H, halo, 6-60C aryl (optionally substituted by group (A)), 2-60C heterocyclyl optionally substituted by group (B'), fluorenyl (optionally substituted by group (D')), 1-50C alkyl (optionally substituted by group (C')), 2-20C alkenyl, 1-30C alkoxy or -L2-N(Ar5)(Ar6);    Ar1,Ar2=6-60C aryl (optionally substituted by group (A)), 2-60C heterocyclyl and optionally substituted by group (B'), fluorenyl (optionally substituted by group (D')), 1-50C alkyl (optionally substituted by group (C')) or -L3-N(Ar7)(Ar8);    L,L1,L2,L3,L4=single bond, 6-60C aryl (optionally substituted by group (A)), fluorenyl (optionally substituted by group (D')), 2-60C heteroaryl, 3-60C cycloalkyl, 3-60C aliphatic group, 6-60C aryl (optionally substituted by group (A));    Ar3-Ar8=6-60C aryl, 2-60C heterocyclyl, 1-50C alkyl or fluorenyl;    group (A)=D, halo, silanyl, boronyl, germanyl, cyano, nitro, 1-20C alkylthio, 1-20C alkoxy, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 6-20C aryl, 2-20C heterocyclyl, 3-20C cycloalkyl, 7-20C arylalkyl or 8-20C arylalkenyl;    group (B')=D, halo, silanyl, cyano, nitro, 1-20C alkoxy, 1-20C alkyl, 2-20C alkenyl, 6-20C aryl, 2-20C heterocyclyl, 3-20C cycloalkyl, 7-20C arylalkyl or 8-20C arylalkenyl;    group (C')=group (B') (excluding D and 3-20C cycloalkyl);and    group (D')=D, halo, silanyl, cyano, 1-20C alkyl, 2-20C alkenyl, 6-20C aryl, 6-20C aryl, 2-20C heterocyclyl or 3-20C cycloalkyl.    "Full definitions are given in the DEFINITIONS (Full Definitions) section". INDEPENDENT CLAIMS are included for the following:    (1) organic electroluminescent device, which contains indoline derivative; and    (2) electronic device, which contains organic electroluminescent device and controller for driving the display device.