A leading representative of figurative sculpture in the first half of the 20th century. In his early years, he was strongly influenced by symbolism and Art Nouveau, while his later works are characterized by Neoclassical forms and a monumental approach.

From 1891 to 1895, he studied at the Technical School of Sculpture and Stonework in Hořice. He then entered the second year of the School of Applied Arts in Prague, where he studied under Stanislav Sucharda. Two years later, he was accepted into the Academy of Fine Arts in the studio of Josef Václav Myslbek, from which he graduated in 1901. He then transferred to the Academy of Arts, Architecture and Design in Prague, where he became an assistant to Stanislav Sucharda. After completing his studies, he received the Hlávka Scholarship in 1902, which enabled him to travel around France, Switzerland, and Germany.

Between 1905 and 1908, he lived in Paris, where he moved within the circle of Impressionist sculptors surrounding Auguste Rodin and Émile-Antoine Bourdelle. Works from this early period, still conceived in the Art Nouveau style with deep symbolism (Somnambula and Mummy), are considered among his finest works. In later years, Kafka returned to realistic depictions in the spirit of the work of his teacher J. V. Myslbek.

In addition to his own work, he was also involved in teaching. After the death of Stanislav Sucharda (1916), he was appointed professor at the School of Applied Arts in Prague and elected rector (1921). In 1925, he became a professor of sculpture at the Academy of Fine Arts in Prague. His students included Jan Lauda, Jaroslav Horejc, and Josef Wagner.

In his artistic work, he collaborated with a number of architects, such as Jan Kotěra, Pavel Janák, and Josef Gočár. Together with the latter, he created a monument to Karel Havlíček Borovský for Německý Brod in 1924 (HB-pc1736_1). His most famous work is probably the monumental equestrian statue of Jan Žižka on Vítkov Hill in Prague (1941, installed in 1950).

During his lifetime, he was a member of numerous associations at home and abroad. From 1898, he was involved in the SVU Mánes, and in Paris he joined the Société du Salon d'Automne (1906), and the Société Nationale des Beaux-Arts (1907). In 1924, he was elected to the Hagenbund in Vienna.